3 files changed, 29 insertions, 23 deletions

diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
index a686f9cd69c..c858f8419eb 100644
--- a/Documentation/kbuild/kconfig-language.txt
+++ b/Documentation/kbuild/kconfig-language.txt
@@ -388,26 +388,3 @@ config FOO
 	depends on BAR && m
 
 limits FOO to module (=m) or disabled (=n).
-
-Kconfig symbol existence
-~~~~~~~~~~~~~~~~~~~~~~~~
-The following two methods produce the same kconfig symbol dependencies
-but differ greatly in kconfig symbol existence (production) in the
-generated config file.
-
-case 1:
-
-config FOO
-	tristate "about foo"
-	depends on BAR
-
-vs. case 2:
-
-if BAR
-config FOO
-	tristate "about foo"
-endif
-
-In case 1, the symbol FOO will always exist in the config file (given
-no other dependencies).  In case 2, the symbol FOO will only exist in
-the config file if BAR is enabled.
diff --git a/Documentation/kbuild/kconfig.txt b/Documentation/kbuild/kconfig.txt
index a09f1a6a830..b8b77bbc784 100644
--- a/Documentation/kbuild/kconfig.txt
+++ b/Documentation/kbuild/kconfig.txt
@@ -46,6 +46,12 @@ KCONFIG_OVERWRITECONFIG
 If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
 break symlinks when .config is a symlink to somewhere else.
 
+CONFIG_
+--------------------------------------------------
+If you set CONFIG_ in the environment, Kconfig will prefix all symbols
+with its value when saving the configuration, instead of using the default,
+"CONFIG_".
+
 ______________________________________________________________________
 Environment variables for '{allyes/allmod/allno/rand}config'
 
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 14c3f4f1b61..5198b742fde 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -1186,6 +1186,29 @@ When kbuild executes, the following steps are followed (roughly):
 		clean-files += *.dtb
 		DTC_FLAGS ?= -p 1024
 
+    dtc_cpp
+	This is just like dtc as describe above, except that the C pre-
+	processor is invoked upon the .dtsp file before compiling the result
+	with dtc.
+
+	In order for build dependencies to work, all files compiled using
+	dtc_cpp must use the C pre-processor's #include functionality and not
+	dtc's /include/ functionality.
+
+	Using the C pre-processor allows use of #define to create named
+	constants. In turn, the #defines will typically appear in a header
+	file, which may be shared with regular C code. Since the dtc language
+	represents a data structure rather than code in C syntax, similar
+	restrictions are placed on a header file included by a device tree
+	file as for a header file included by an assembly language file.
+	In particular, the C pre-processor is passed -x assembler-with-cpp,
+	which sets macro __ASSEMBLY__. __DTS__ is also set. These allow header
+	files to restrict their content to that compatible with device tree
+	source.
+
+	A central rule exists to create $(obj)/%.dtb from $(src)/%.dtsp;
+	architecture Makefiles do no need to explicitly write out that rule.
+
 --- 6.8 Custom kbuild commands
 
 	When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand