docs: ABI: make it parse ABI/stable as ReST-compatible files

Now that the stable ABI files are compatible with ReST,
parse them without converting complex descriptions as literal
blocks nor escaping special characters.

Please notice that escaping special characters will probably
be needed at descriptions, at least for the asterisk character.
Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/59ccbaa75ff05f23e701dd9a0bbe118e9343a553.1604042072.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/admin-guide/abi-stable.rst

@@ -11,3 +11,4 @@ Most interfaces (like syscalls) are expected to never change and always
 be available.
 
 .. kernel-abi:: $srctree/Documentation/ABI/stable
+   :rst:

Documentation/sphinx/kernel_abi.py

@@ -73,12 +73,13 @@ class KernelCmd(Directive):
     u"""KernelABI (``kernel-abi``) directive"""
 
     required_arguments = 1
-    optional_arguments = 0
+    optional_arguments = 2
     has_content = False
     final_argument_whitespace = True
 
     option_spec = {
-        "debug"     : directives.flag
+        "debug"     : directives.flag,
+        "rst"       : directives.unchanged
     }
 
     def run(self):
@@ -92,6 +93,9 @@ class KernelCmd(Directive):
         cmd = "get_abi.pl rest --enable-lineno --dir "
         cmd += self.arguments[0]
 
+        if 'rst' in self.options:
+            cmd += " --rst-source"
+
         srctree = path.abspath(os.environ["srctree"])
 
         fname = cmd