scripts/kernel-doc.py: Properly handle Werror and exit codes

The original kernel-doc script has a logic to return warnings
as errors, and to report the number of warnings found, if in
verbose mode.

Implement it to be fully compatible with the original script.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/de33b0cebd9fdf82d8b221bcfe41db7269286222.1744106242.git.mchehab+huawei@kernel.org

scripts/kernel-doc.py

@@ -78,8 +78,6 @@
 #    Yacine Belkadi <yacine.belkadi.1@gmail.com>
 #    Yujie Liu <yujie.liu@intel.com>
 
-# TODO: implement warning filtering
-
 """
 kernel_doc
 ==========
@@ -295,6 +293,22 @@ def main():
         if msg:
             print(msg)
 
+    error_count = kfiles.errors
+    if not error_count:
+        sys.exit(0)
+
+    if args.werror:
+        print(f"{error_count} warnings as errors")
+        sys.exit(error_count)
+
+    if args.verbose:
+        print(f"{error_count} errors")
+
+    if args.none:
+        sys.exit(0)
+
+    sys.exit(error_count)
+
 
 # Call main method
 if __name__ == "__main__":