docs: conf.py: fix c:function support with Sphinx 3.x

Sphinx C parser for the C domain is now more pedantic when
trying to identify the function types. That prevents scope
macros to be used as type defines.

Yet, since 3.0.2, it is possible to provide it a list of
such macros. Add them, in order to solve several Sphinx 3.x
warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/conf.py

@@ -47,9 +47,68 @@ extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include',
 #
 if major >= 3:
     sys.stderr.write('''WARNING: The kernel documentation build process
-	does not work correctly with Sphinx v3.0 and above.  Expect errors
-	in the generated output.
-	''')
+        does not work correctly with Sphinx v3.0 and above.  Expect errors
+        in the generated output.
+        ''')
+    if minor > 0 or patch >= 2:
+        # Sphinx c function parser is more pedantic with regards to type
+        # checking. Due to that, having macros at c:function cause problems.
+        # Those needed to be scaped by using c_id_attributes[] array
+        c_id_attributes = [
+            # GCC Compiler types not parsed by Sphinx:
+            "__restrict__",
+
+            # include/linux/compiler_types.h:
+            "__iomem",
+            "__kernel",
+            "noinstr",
+            "notrace",
+            "__percpu",
+            "__rcu",
+            "__user",
+
+            # include/linux/compiler_attributes.h:
+            "__alias",
+            "__aligned",
+            "__aligned_largest",
+            "__always_inline",
+            "__assume_aligned",
+            "__cold",
+            "__attribute_const__",
+            "__copy",
+            "__pure",
+            "__designated_init",
+            "__visible",
+            "__printf",
+            "__scanf",
+            "__gnu_inline",
+            "__malloc",
+            "__mode",
+            "__no_caller_saved_registers",
+            "__noclone",
+            "__nonstring",
+            "__noreturn",
+            "__packed",
+            "__pure",
+            "__section",
+            "__always_unused",
+            "__maybe_unused",
+            "__used",
+            "__weak",
+            "noinline",
+
+            # include/linux/memblock.h:
+            "__init_memblock",
+            "__meminit",
+
+            # include/linux/init.h:
+            "__init",
+            "__ref",
+
+            # include/linux/linkage.h:
+            "asmlinkage",
+        ]
+
 else:
     extensions.append('cdomain')