docs: load_config.py: avoid needing a conf.py just due to LaTeX docs

Right now, for every directory that we need to have LaTeX output,
a conf.py file is required.

That causes an extra overhead and it is actually a hack, as
the latex_documents line there are usually a copy of the ones
that are there already at the main conf.py.

So, instead, re-use the global latex_documents var, just
adjusting the path to be relative ones.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/sphinx/load_config.py

@@ -21,6 +21,29 @@ def loadConfig(namespace):
         and os.path.normpath(namespace["__file__"]) != os.path.normpath(config_file) ):
         config_file = os.path.abspath(config_file)
 
+        # Let's avoid one conf.py file just due to latex_documents
+        start = config_file.find('Documentation/')
+        if start >= 0:
+            start = config_file.find('/', start + 1)
+
+        end = config_file.rfind('/')
+        if start >= 0 and end > 0:
+            dir = config_file[start + 1:end]
+
+            print("source directory: %s" % dir)
+            new_latex_docs = []
+            latex_documents = namespace['latex_documents']
+
+            for l in latex_documents:
+                if l[0].find(dir) == 0:
+                    has = True
+                    fn = l[0][len(dir) + 1:]
+                    new_latex_docs.append((fn, l[1], l[2], l[3], l[4]))
+                    break
+
+            namespace['latex_documents'] = new_latex_docs
+
+        # If there is an extra conf.py file, load it
         if os.path.isfile(config_file):
             sys.stdout.write("load additional sphinx-config: %s\n" % config_file)
             config = namespace.copy()
@@ -29,4 +52,6 @@ def loadConfig(namespace):
             del config['__file__']
             namespace.update(config)
         else:
-            sys.stderr.write("WARNING: additional sphinx-config not found: %s\n" % config_file)
+            config = namespace.copy()
+            config['tags'].add("subproject")
+            namespace.update(config)