doc-rst: add boilerplate to customize c-domain

Add a sphinx-extension to customize the sphinx c-domain.  No functional
changes right yet, just the boilerplate code.
Signed-off-by: Markus Heiser <markus.heiser@darmarIT.de>
[ jc: coding-style tweak ]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/conf.py

@@ -34,7 +34,7 @@ from load_config import loadConfig
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = ['kernel-doc', 'rstFlatTable', 'kernel_include']
+extensions = ['kernel-doc', 'rstFlatTable', 'kernel_include', 'cdomain']
 
 # The name of the math extension changed on Sphinx 1.4
 if minor > 3:

Documentation/sphinx/cdomain.py

+# -*- coding: utf-8; mode: python -*-
+u"""
+    cdomain
+    ~~~~~~~
+
+    Replacement for the sphinx c-domain.
+
+    :copyright:  Copyright (C) 2016  Markus Heiser
+    :license:    GPL Version 2, June 1991 see Linux/COPYING for details.
+"""
+
+from sphinx.domains.c import CObject as Base_CObject
+from sphinx.domains.c import CDomain as Base_CDomain
+
+__version__  = '1.0'
+
+def setup(app):
+
+    app.override_domain(CDomain)
+
+    return dict(
+        version = __version__,
+        parallel_read_safe = True,
+        parallel_write_safe = True
+    )
+
+class CObject(Base_CObject):
+
+    """
+    Description of a C language object.
+    """
+
+class CDomain(Base_CDomain):
+
+    """C language domain."""
+    name = 'c'
+    label = 'C'
+    directives = {
+        'function': CObject,
+        'member':   CObject,
+        'macro':    CObject,
+        'type':     CObject,
+        'var':      CObject,
+    }