parse-headers.pl: add documentation for this script

Provide a man page for parse-headers.pl, describing
how to use it.

The documentation on ReST format was generated via pod2rst:
	http://search.cpan.org/~dowens/Pod-POM-View-Restructured-0.02/bin/pod2rst

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/doc-guide/index.rst

@@ -9,6 +9,7 @@ How to write kernel documentation
 
    sphinx.rst
    kernel-doc.rst
+   parse-headers.rst
    docbook.rst
 
 .. only::  subproject and html

Documentation/doc-guide/parse-headers.rst

@@ -0,0 +1,186 @@
+================
+parse_headers.pl
+================
+
+****
+NAME
+****
+
+
+parse_headers.pl - parse a C file, in order to identify functions, structs,
+enums and defines and create cross-references to a Sphinx book.
+
+
+********
+SYNOPSIS
+********
+
+
+\ **parse_headers.pl**\  [<options>] <C_FILE> <OUT_FILE> [<EXCEPTIONS_FILE>]
+
+Where <options> can be: --debug, --help or --man.
+
+
+*******
+OPTIONS
+*******
+
+
+
+\ **--debug**\
+
+ Put the script in verbose mode, useful for debugging.
+
+
+
+\ **--help**\
+
+ Prints a brief help message and exits.
+
+
+
+\ **--man**\
+
+ Prints the manual page and exits.
+
+
+
+
+***********
+DESCRIPTION
+***********
+
+
+Convert a C header or source file (C_FILE), into a ReStructured Text
+included via ..parsed-literal block with cross-references for the
+documentation files that describe the API. It accepts an optional
+EXCEPTIONS_FILE with describes what elements will be either ignored or
+be pointed to a non-default reference.
+
+The output is written at the (OUT_FILE).
+
+It is capable of identifying defines, functions, structs, typedefs,
+enums and enum symbols and create cross-references for all of them.
+It is also capable of distinguish #define used for specifying a Linux
+ioctl.
+
+The EXCEPTIONS_FILE contain two types of statements: \ **ignore**\  or \ **replace**\ .
+
+The syntax for the ignore tag is:
+
+
+ignore \ **type**\  \ **name**\
+
+The \ **ignore**\  means that it won't generate cross references for a
+\ **name**\  symbol of type \ **type**\ .
+
+The syntax for the replace tag is:
+
+
+replace \ **type**\  \ **name**\  \ **new_value**\
+
+The \ **replace**\  means that it will generate cross references for a
+\ **name**\  symbol of type \ **type**\ , but, instead of using the default
+replacement rule, it will use \ **new_value**\ .
+
+For both statements, \ **type**\  can be either one of the following:
+
+
+\ **ioctl**\
+
+ The ignore or replace statement will apply to ioctl definitions like:
+
+ #define	VIDIOC_DBG_S_REGISTER 	 _IOW('V', 79, struct v4l2_dbg_register)
+
+
+
+\ **define**\
+
+ The ignore or replace statement will apply to any other #define found
+ at C_FILE.
+
+
+
+\ **typedef**\
+
+ The ignore or replace statement will apply to typedef statements at C_FILE.
+
+
+
+\ **struct**\
+
+ The ignore or replace statement will apply to the name of struct statements
+ at C_FILE.
+
+
+
+\ **enum**\
+
+ The ignore or replace statement will apply to the name of enum statements
+ at C_FILE.
+
+
+
+\ **symbol**\
+
+ The ignore or replace statement will apply to the name of enum statements
+ at C_FILE.
+
+ For replace statements, \ **new_value**\  will automatically use :c:type:
+ references for \ **typedef**\ , \ **enum**\  and \ **struct**\  types. It will use :ref:
+ for \ **ioctl**\ , \ **define**\  and \ **symbol**\  types. The type of reference can
+ also be explicitly defined at the replace statement.
+
+
+
+
+********
+EXAMPLES
+********
+
+
+ignore define _VIDEODEV2_H
+
+
+Ignore a #define _VIDEODEV2_H at the C_FILE.
+
+ignore symbol PRIVATE
+
+
+On a struct like:
+
+enum foo { BAR1, BAR2, PRIVATE };
+
+It won't generate cross-references for \ **PRIVATE**\ .
+
+replace symbol BAR1 :c:type:\`foo\`
+replace symbol BAR2 :c:type:\`foo\`
+
+
+On a struct like:
+
+enum foo { BAR1, BAR2, PRIVATE };
+
+It will make the BAR1 and BAR2 enum symbols to cross reference the foo
+symbol at the C domain.
+
+
+****
+BUGS
+****
+
+
+Report bugs to Mauro Carvalho Chehab <mchehab@s-opensource.com>
+
+
+*********
+COPYRIGHT
+*********
+
+
+Copyright (c) 2016 by Mauro Carvalho Chehab <mchehab@s-opensource.com>.
+
+License GPLv2: GNU GPL version 2 <http://gnu.org/licenses/gpl.html>.
+
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law.