doc: Add minimal glossary

One of the current issues with the documentation is that terms and
abbreviations are frequently redefined. For example, we might have
a sentence like "... the SCP (System Control Processor) will ...".

These definitions might be repeated several times across pages, or
even within the same document. Equally, some of these abbreviations
are missed and are never expanded.

Sphinx provides a :term: keyword that takes some text and,
if that text is defined in a glossary document, links to its glossary
entry. Using this functionality will prevent repeated definitions
and will make the docs more maintainable by using a single
definition source.

The glossary added in this patch was created from a quick scrub of
the source code - there may be missing entries. The SDEI abbreviation
was used as an example.

Note that a global_substitutions file was created. This file contains
the RST 'replace' statements that convert plain text terms into linked
terms (by adding the ':term:' keyword to them). An example is:

.. |TF-A| replace:: :term:`TF-A`

The 'rst_prolog' variable in conf.py is used to inject this list of
replacements into each page. Terms must be surrounded with the pipe
character to be turned into links - this means that we can still
prevent certain terms from being linked if we don't want them to be.

Change-Id: I87010ed9cfa4a60011a9b4a431b98cb4bb7baa28
Signed-off-by: Paul Beesley <paul.beesley@arm.com>

7 files changed, 273 insertions, 37 deletions

diff --git a/docs/change-log.rst b/docs/change-log.rst
index 1b6a481f..bbd7feca 100644
--- a/docs/change-log.rst
+++ b/docs/change-log.rst
@@ -294,12 +294,12 @@ Changed
 
 - SDEI
    - Added support for unconditionally resuming secure world execution after
-     SDEI event processing completes
+     |SDEI| event processing completes
 
-     SDEI interrupts, although targeting EL3, occur on behalf of the non-secure
+     |SDEI| interrupts, although targeting EL3, occur on behalf of the non-secure
      world, and may have higher priority than secure world
      interrupts. Therefore they might preempt secure execution and yield
-     execution to the non-secure SDEI handler. Upon completion of SDEI event
+     execution to the non-secure |SDEI| handler. Upon completion of |SDEI| event
      handling, resume secure execution if it was preempted.
 
 - Translation Tables (XLAT)
@@ -501,7 +501,7 @@ New Features
 
    -  Implement dynamic mitigation for CVE-2018-3639 on Cortex-A76
 
-   -  Ensure SDEI handler executes with CVE-2018-3639 mitigation enabled
+   -  Ensure |SDEI| handler executes with CVE-2018-3639 mitigation enabled
 
 -  Introduce RAS handling on AArch64
 
@@ -621,7 +621,7 @@ New Features
 
    -  Introduce jump primitives for BL31
 
-   -  Mask events after CPU wakeup in SDEI dispatcher to conform to the
+   -  Mask events after CPU wakeup in |SDEI| dispatcher to conform to the
       specification
 
 -  Misc TF-A Core Common Code Enhancements
@@ -785,8 +785,8 @@ New features
       management and security services. The SPM is the firmware component that
       is responsible for managing a Secure Partition.
 
-   -  SDEI dispatcher: Support for interrupt-based SDEI events and all
-      interfaces as defined by the SDEI specification v1.0, see
+   -  SDEI dispatcher: Support for interrupt-based |SDEI| events and all
+      interfaces as defined by the |SDEI| specification v1.0, see
       `SDEI Specification`_
 
    -  Exception Handling Framework (EHF): Framework that allows dispatching of
diff --git a/docs/components/exception-handling.rst b/docs/components/exception-handling.rst
index 2452e06a..a89a05c9 100644
--- a/docs/components/exception-handling.rst
+++ b/docs/components/exception-handling.rst
@@ -1,9 +1,6 @@
 Exception Handling Framework
 ============================
 
-.. |EHF| replace:: Exception Handling Framework
-.. |TF-A| replace:: Trusted Firmware-A
-
 This document describes various aspects of handling exceptions by Runtime
 Firmware (BL31) that are targeted at EL3, other than SMCs. The |EHF| takes care
 of the following exceptions when targeted at EL3:
@@ -48,11 +45,11 @@ exceptions are targeted at and handled in EL3. For instance:
 
 -  The Arm `SDEI specification`_ defines interfaces through which Normal world
    interacts with the Runtime Firmware in order to request notification of
-   system events. The SDEI specification requires that these events are notified
-   even when the Normal world executes with the exceptions masked. This too
-   implies that firmware-first handling is required, where the events are first
-   received by the EL3 firmware, and then dispatched to Normal world through
-   purely software mechanism.
+   system events. The |SDEI| specification requires that these events are
+   notified even when the Normal world executes with the exceptions masked. This
+   too implies that firmware-first handling is required, where the events are
+   first received by the EL3 firmware, and then dispatched to Normal world
+   through purely software mechanism.
 
 For |TF-A|, firmware-first handling means that asynchronous exceptions are
 suitably routed to EL3, and the Runtime Firmware (BL31) is extended to include
@@ -73,8 +70,8 @@ choose to:
    processing of the error to dedicated software stack running at lower secure
    ELs (as above); additionally, the Normal world may also be required to
    participate in the handling, or be notified of such events (for example, as
-   an SDEI event). In this scheme, exception handling potentially and maximally
-   spans all ELs in both Secure and Normal worlds.
+   an |SDEI| event). In this scheme, exception handling potentially and
+   maximally spans all ELs in both Secure and Normal worlds.
 
 On any given system, all of the above handling models may be employed
 independently depending on platform choice and the nature of the exception
@@ -603,8 +600,8 @@ should carefully consider the assignment of priorities to dispatchers integrated
 into runtime firmware. The platform should sensibly delineate priority to
 various dispatchers according to their nature. In particular, dispatchers of
 critical nature (RAS, for example) should be assigned higher priority than
-others (SDEI, for example); and within SDEI, Critical priority SDEI should be
-assigned higher priority than Normal ones.
+others (|SDEI|, for example); and within |SDEI|, Critical priority
+|SDEI| should be assigned higher priority than Normal ones.
 
 Limitations
 -----------
diff --git a/docs/conf.py b/docs/conf.py
index 0fcc50d2..697b8711 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -9,6 +9,8 @@
 #
 # See the options documentation at http://www.sphinx-doc.org/en/master/config
 
+import os
+
 # -- Project information -----------------------------------------------------
 
 project = 'Trusted Firmware-A'
@@ -16,7 +18,6 @@ project = 'Trusted Firmware-A'
 version = '2.1'
 release = version # We don't need these to be distinct
 
-
 # -- General configuration ---------------------------------------------------
 
 # Add any Sphinx extension module names here, as strings. They can be
@@ -48,6 +49,10 @@ exclude_patterns = []
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'
 
+# Load the contents of the global substitutions file into the 'rst_prolog'
+# variable. This ensures that the substitutions are all inserted into each page.
+with open('global_substitutions.txt', 'r') as subs:
+  rst_prolog = subs.read()
 
 # -- Options for HTML output -------------------------------------------------
 
diff --git a/docs/getting_started/porting-guide.rst b/docs/getting_started/porting-guide.rst
index 458615ec..5be8c152 100644
--- a/docs/getting_started/porting-guide.rst
+++ b/docs/getting_started/porting-guide.rst
@@ -1840,7 +1840,7 @@ line boundary.
 SDEI porting requirements
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The SDEI dispatcher requires the platform to provide the following macros
+The |SDEI| dispatcher requires the platform to provide the following macros
 and functions, of which some are optional, and some others mandatory.
 
 Macros
@@ -1850,19 +1850,19 @@ Macro: PLAT_SDEI_NORMAL_PRI [mandatory]
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This macro must be defined to the EL3 exception priority level associated with
-Normal SDEI events on the platform. This must have a higher value (therefore of
-lower priority) than ``PLAT_SDEI_CRITICAL_PRI``.
+Normal |SDEI| events on the platform. This must have a higher value
+(therefore of lower priority) than ``PLAT_SDEI_CRITICAL_PRI``.
 
 Macro: PLAT_SDEI_CRITICAL_PRI [mandatory]
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This macro must be defined to the EL3 exception priority level associated with
-Critical SDEI events on the platform. This must have a lower value (therefore of
-higher priority) than ``PLAT_SDEI_NORMAL_PRI``.
+Critical |SDEI| events on the platform. This must have a lower value
+(therefore of higher priority) than ``PLAT_SDEI_NORMAL_PRI``.
 
-**Note**: SDEI exception priorities must be the lowest among Secure priorities.
-Among the SDEI exceptions, Critical SDEI priority must be higher than Normal
-SDEI priority.
+**Note**: |SDEI| exception priorities must be the lowest among Secure
+priorities. Among the |SDEI| exceptions, Critical |SDEI| priority must
+be higher than Normal |SDEI| priority.
 
 Functions
 .........
@@ -1876,10 +1876,10 @@ Function: int plat_sdei_validate_entry_point(uintptr_t ep) [optional]
   Return: int
 
 This function validates the address of client entry points provided for both
-event registration and *Complete and Resume* SDEI calls. The function takes one
-argument, which is the address of the handler the SDEI client requested to
-register. The function must return ``0`` for successful validation, or ``-1``
-upon failure.
+event registration and *Complete and Resume* |SDEI| calls. The function
+takes one argument, which is the address of the handler the |SDEI| client
+requested to register. The function must return ``0`` for successful validation,
+or ``-1`` upon failure.
 
 The default implementation always returns ``0``. On Arm platforms, this function
 is implemented to translate the entry point to physical address, and further to
@@ -1894,11 +1894,12 @@ Function: void plat_sdei_handle_masked_trigger(uint64_t mpidr, unsigned int intr
   Argument: unsigned int
   Return: void
 
-SDEI specification requires that a PE comes out of reset with the events masked.
-The client therefore is expected to call ``PE_UNMASK`` to unmask SDEI events on
-the PE. No SDEI events can be dispatched until such time.
+|SDEI| specification requires that a PE comes out of reset with the events
+masked. The client therefore is expected to call ``PE_UNMASK`` to unmask
+|SDEI| events on the PE. No |SDEI| events can be dispatched until such
+time.
 
-Should a PE receive an interrupt that was bound to an SDEI event while the
+Should a PE receive an interrupt that was bound to an |SDEI| event while the
 events are masked on the PE, the dispatcher implementation invokes the function
 ``plat_sdei_handle_masked_trigger``. The MPIDR of the PE that received the
 interrupt and the interrupt ID are passed as parameters.
diff --git a/docs/global_substitutions.txt b/docs/global_substitutions.txt
new file mode 100644
index 00000000..242e62c7
--- /dev/null
+++ b/docs/global_substitutions.txt
@@ -0,0 +1,55 @@
+.. |AArch32| replace:: :term:`AArch32`
+.. |AArch64| replace:: :term:`AArch64`
+.. |API| replace:: :term:`API`
+.. |CoT| replace:: :term:`CoT`
+.. |COT| replace:: :term:`COT`
+.. |CSS| replace:: :term:`CSS`
+.. |CVE| replace:: :term:`CVE`
+.. |DS-5| replace:: :term:`DS-5`
+.. |DT| replace:: :term:`DT`
+.. |EL| replace:: :term:`EL`
+.. |EHF| replace:: :term:`EHF`
+.. |FDT| replace:: :term:`FDT`
+.. |FIP| replace:: :term:`FIP`
+.. |FVP| replace:: :term:`FVP`
+.. |FWU| replace:: :term:`FWU`
+.. |GIC| replace:: :term:`GIC`
+.. |ISA| replace:: :term:`ISA`
+.. |Linaro| replace:: :term:`Linaro`
+.. |MMU| replace:: :term:`MMU`
+.. |MPAM| replace:: :term:`MPAM`
+.. |MPIDR| replace:: :term:`MPIDR`
+.. |OEN| replace:: :term:`OEN`
+.. |OP-TEE| replace:: :term:`OP-TEE`
+.. |OTE| replace:: :term:`OTE`
+.. |PDD| replace:: :term:`PDD`
+.. |PMF| replace:: :term:`PMF`
+.. |PSCI| replace:: :term:`PSCI`
+.. |RAS| replace:: :term:`RAS`
+.. |ROT| replace:: :term:`ROT`
+.. |SCMI| replace:: :term:`SCMI`
+.. |SCP| replace:: :term:`SCP`
+.. |SDEI| replace:: :term:`SDEI`
+.. |SDS| replace:: :term:`SDS`
+.. |SEA| replace:: :term:`SEA`
+.. |SiP| replace:: :term:`SiP`
+.. |SIP| replace:: :term:`SIP`
+.. |SMC| replace:: :term:`SMC`
+.. |SMCCC| replace:: :term:`SMCCC`
+.. |SoC| replace:: :term:`SoC`
+.. |SP| replace:: :term:`SP`
+.. |SPD| replace:: :term:`SPD`
+.. |SPM| replace:: :term:`SPM`
+.. |SVE| replace:: :term:`SVE`
+.. |TBB| replace:: :term:`TBB`
+.. |TBBR| replace:: :term:`TBBR`
+.. |TEE| replace:: :term:`TEE`
+.. |TF-A| replace:: :term:`TF-A`
+.. |TF-M| replace:: :term:`TF-M`
+.. |TLB| replace:: :term:`TLB`
+.. |TLK| replace:: :term:`TLK`
+.. |TSP| replace:: :term:`TSP`
+.. |TZC| replace:: :term:`TZC`
+.. |UEFI| replace:: :term:`UEFI`
+.. |WDOG| replace:: :term:`WDOG`
+.. |XLAT| replace:: :term:`XLAT`
\ No newline at end of file
diff --git a/docs/glossary.rst b/docs/glossary.rst
new file mode 100644
index 00000000..afe0acf7
--- /dev/null
+++ b/docs/glossary.rst
@@ -0,0 +1,177 @@
+Glossary
+========
+
+This glossary provides definitions for terms and abbreviations used in the TF-A
+documentation.
+
+You can find additional definitions in the `Arm Glossary`_.
+
+.. glossary::
+   :sorted:
+
+   AArch32
+      32-bit execution state of the ARMv8 ISA
+
+   AArch64
+      64-bit execution state of the ARMv8 ISA
+
+   API
+      Application Programming Interface
+
+   CoT
+   COT
+      Chain of Trust
+
+   CSS
+      Compute Sub-System
+
+   CVE
+      Common Vulnerabilities and Exposures. A CVE document is commonly used to
+      describe a publicly-known security vulnerability.
+
+   DS-5
+      Arm Development Studio 5
+
+   DT
+      Device Tree
+
+   EL
+      Exception Level
+
+   EHF
+      Exception Handling Framework
+
+   FDT
+      Flattened Device Tree
+
+   FIP
+      Firmware Image Package
+
+   FVP
+      Fixed Virtual Platform
+
+   FWU
+      FirmWare Update
+
+   GIC
+      Generic Interrupt Controller
+
+   ISA
+      Instruction Set Architecture
+
+   Linaro
+      A collaborative engineering organization consolidating
+      and optimizing open source software and tools for the Arm architecture.
+
+   MMU
+      Memory Management Unit
+
+   MPAM
+      Memory Partitioning And Monitoring. An optional Armv8.4 extension.
+
+   MPIDR
+      Multiprocessor Affinity Register
+
+   OEN
+      Owning Entity Number
+
+   OP-TEE
+      Open Portable Trusted Execution Environment. An example of a :term:`TEE`
+
+   OTE
+      Open-source Trusted Execution Environment
+
+   PDD
+      Platform Design Document
+
+   PMF
+      Performance Measurement Framework
+
+   PSCI
+      Power State Coordination Interface
+
+   RAS
+      Reliability, Availability, and Serviceability extensions. A mandatory
+      extension for the Armv8.2 architecture and later. An optional extension to
+      the base Armv8 architecture.
+
+   ROT
+      Root of Trust
+
+   SCMI
+      System Control and Management Interface
+
+   SCP
+      System Control Processor
+
+   SDEI
+      Software Delegated Exception Interface
+
+   SDS
+      Shared Data Storage
+
+   SEA
+      Synchronous External Abort
+
+   SiP
+   SIP
+      Silicon Provider
+
+   SMC
+      Secure Monitor Call
+
+   SMCCC
+      :term:`SMC` Calling Convention
+
+   SoC
+      System on Chip
+
+   SP
+      Secure Partition
+
+   SPD
+      Secure Payload Dispatcher
+
+   SPM
+      Secure Partition Manager
+
+   SVE
+      Scalable Vector Extension
+
+   TBB
+      Trusted Board Boot
+
+   TBBR
+      Trusted Board Boot Requirements
+
+   TEE
+      Trusted Execution Environment
+
+   TF-A
+      Trusted Firmware-A
+
+   TF-M
+      Trusted Firmware-M
+
+   TLB
+      Translation Lookaside Buffer
+
+   TLK
+      Trusted Little Kernel. A Trusted OS from NVIDIA.
+
+   TSP
+      Test Secure Payload
+
+   TZC
+      TrustZone Controller
+
+   UEFI
+      Unified Extensible Firmware Interface
+
+   WDOG
+      Watchdog
+
+   XLAT
+      Translation (abbr.). For example, "XLAT table".
+
+.. _`Arm Glossary`: https://developer.arm.com/support/arm-glossary
\ No newline at end of file
diff --git a/docs/index.rst b/docs/index.rst
index f23b948d..b0eff61d 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -15,6 +15,7 @@ Trusted Firmware-A Documentation
    security_advisories/index
    change-log
    acknowledgements
+   glossary
    maintainers
    license
 
@@ -102,7 +103,7 @@ Functionality
       Secure-EL0, which can be used to implement simple management and
       security services.
 
-   -  An SDEI dispatcher to route interrupt-based SDEI events.
+   -  An |SDEI| dispatcher to route interrupt-based |SDEI| events.
 
    -  An Exception Handling Framework (EHF) that allows dispatching of EL3
       interrupts to their registered handlers, to facilitate firmware-first