[PATCH v3] docs: kerneldoc.py: preserve headings in kernel-doc output

[Karl Mehltretter <kmehltretter@gmail.com>]

kerneldoc.py parses extracted ReST into a detached section node while
retaining the surrounding title hierarchy. Docutils 0.21.2 silently drops
affected sections; 0.22.4 reports:

  Documentation/networking/kapi:107:
  ../include/net/net_shaper.h:75:
  ERROR: A level 3 section cannot be used here.

The same issue drops three Xe DRM RAS headings already in mainline.

Use nested_parse_with_titles() to give kernel-doc output an independent
title hierarchy.

Fixes: 2404dad1f67f ("doc: Cope with the deprecation of AutoReporter")
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
Reposted as a standalone documentation patch at Jakub's suggestion:
https://lore.kernel.org/r/20260925120152.09ef180c@kernel.org/

Changes since v2:
- Route the patch to the documentation maintainers without a net-next tag.
- Add Randy's Acked-by and Tested-by tags. No code changes.

 Documentation/sphinx/kerneldoc.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/sphinx/kerneldoc.py b/Documentation/sphinx/kerneldoc.py
index c1cadb4eb0997..9986df33e37ea 100644
--- a/Documentation/sphinx/kerneldoc.py
+++ b/Documentation/sphinx/kerneldoc.py
@@ -38,6 +38,7 @@ from docutils.statemachine import ViewList
 from docutils.parsers.rst import directives, Directive
 import sphinx
 from sphinx.util.docutils import switch_source_input
+from sphinx.util.nodes import nested_parse_with_titles
 from sphinx.util import logging
 from pprint import pformat
 
@@ -252,7 +253,7 @@ class KernelDocDirective(Directive):
 
     def do_parse(self, result, node):
         with switch_source_input(self.state, result):
-            self.state.nested_parse(result, 0, node, match_titles=1)
+            nested_parse_with_titles(self.state, result, node)
 
 def setup_kfiles(app):
     global kfiles
-- 
2.53.0