doc: doc generation: remove breathe references

Remove the references to the breathe extension in the
Schematic of the documentation build process graph and
the filtering expected warnings section.

Signed-off-by: Simon Hein <[email protected]>

Author: simhein

doc/contribute/documentation/generation.rst

@@ -52,7 +52,7 @@ The project's documentation contains the following items:
       header [shape="rectangle" label="c header\ncomments"]
       xml [shape="rectangle" label="XML"]
       html [shape="rectangle" label="HTML\nweb site"]
-      sphinx[shape="ellipse" label="sphinx +\nbreathe,\ndocutils"]
+      sphinx[shape="ellipse" label="sphinx +\ndocutils"]
       images -> sphinx
       rst -> sphinx
       conf -> sphinx
@@ -65,8 +65,8 @@ The project's documentation contains the following items:
 
 
 The reStructuredText files are processed by the Sphinx documentation system,
-and make use of the breathe extension for including the doxygen-generated API
-material.  Additional tools are required to generate the
+and make use of the doxygen-generated API material.
+Additional tools are required to generate the
 documentation locally, as described in the following sections.
 
 .. _documentation-processors:
@@ -242,24 +242,6 @@ build the documentation directly from there:
    # To generate PDF output
    make pdf
 
-Filtering expected warnings
-***************************
-
-There are some known issues with Sphinx/Breathe that generate Sphinx warnings
-even though the input is valid C code. While these issues are being considered
-for fixing we have created a Sphinx extension that allows to filter them out
-based on a set of regular expressions. The extension is named
-``zephyr.warnings_filter`` and it is located at
-``doc/_extensions/zephyr/warnings_filter.py``. The warnings to be filtered out
-can be added to the ``doc/known-warnings.txt`` file.
-
-The most common warning reported by Sphinx/Breathe is related to duplicate C
-declarations. This warning may be caused by different Sphinx/Breathe issues:
-
-- Multiple declarations of the same object are not supported
-- Different objects (e.g. a struct and a function) can not share the same name
-- Nested elements (e.g. in a struct or union) can not share the same name
-
 Developer-mode Document Building
 ********************************