doc: add configuration reference and remove parameter details

It is easy to have out-of-date comments since Sphinx settings evolve
(defaults, behavior...). A reference to the official documentation is
provided at the top of the file instead.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

doc/conf.py

@@ -1,16 +1,5 @@
-# -*- coding: utf-8 -*-
-#
-# Zephyr documentation build configuration file, created by
-# sphinx-quickstart on Fri May  8 11:43:01 2015.
-#
-# This file is execfile()d with the current directory set to its
-# containing dir.
-#
-# Note that not all possible configuration values are present in this
-# autogenerated file.
-#
-# All configuration values have a default; values that are commented out
-# serve to show the default.
+# Zephyr documentation build configuration file.
+# Reference: https://www.sphinx-doc.org/en/master/usage/configuration.html
 
 import sys
 import os
@@ -44,9 +33,6 @@ except ImportError:
 
 # -- General configuration ------------------------------------------------
 
-# Add any Sphinx extension module names here, as strings. They can be
-# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
-# ones.
 extensions = [
     'breathe', 'sphinx.ext.todo',
     'sphinx.ext.extlinks',
@@ -63,10 +49,8 @@ extensions = [
 if tags.has("svgconvert"):  # pylint: disable=undefined-variable
     extensions.append('sphinxcontrib.rsvgconverter')
 
-# Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
 
-# General information about the project.
 project = u'Zephyr Project'
 copyright = u'2015-2021 Zephyr Project members and individual contributors'
 author = u'The Zephyr Project'
@@ -108,26 +92,19 @@ finally:
 # Usually you set "language" from the command line for these cases.
 language = None
 
-# List of patterns, relative to source directory, that match files and
-# directories to ignore when looking for source files.
 exclude_patterns = ['_build']
 if not west_found:
     exclude_patterns.append('**/*west-apis*')
 else:
     exclude_patterns.append('**/*west-not-found*')
 
-# The reST default role (used for this markup: `text`) to use for all
-# documents.
-
 # This change will allow us to use bare back-tick notation to let
 # Sphinx hunt for a reference, starting with normal "document"
 # references such as :ref:, but also including :c: and :cpp: domains
 # (potentially) helping with API (doxygen) references simply by using
 # `name`
-
 default_role = 'any'
 
-# The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'
 
 # Additional lexer for Pygments (syntax highlighting)
@@ -135,7 +112,6 @@ from lexer.DtsLexer import DtsLexer
 from sphinx.highlighting import lexers
 lexers['DTS'] = DtsLexer()
 
-# If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = False
 
 rst_epilog = """
@@ -158,42 +134,24 @@ else:
     is_release = False
     docs_title = 'Docs / Latest'
 
-# The name for this set of Sphinx documents.  If None, it defaults to
-# "<project> v<release> documentation".
 html_title = "Zephyr Project Documentation"
 
-# The name of an image file (relative to this directory) to place at the top
-# of the sidebar.
 html_logo = 'images/Zephyr-Kite-logo.png'
 
-# The name of an image file (within the static path) to use as favicon of the
-# docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
-# pixels large.
 html_favicon = 'images/zp_favicon.png'
 
-# Add any paths that contain custom static files (such as style sheets) here,
-# relative to this directory. They are copied after the builtin static files,
-# so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['{}/doc/_static'.format(ZEPHYR_BASE)]
 
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
 html_last_updated_fmt = '%b %d, %Y'
 
-# If false, no module index is generated.
 html_domain_indices = False
 
-# If true, the index is split into individual pages for each letter.
 html_split_index = True
 
-# If true, links to the reST sources are added to the pages.
 html_show_sourcelink = False
 
-# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
 html_show_sphinx = False
 
-# The name of a javascript file (relative to the configuration directory) that
-# implements a search results scorer. If empty, the default will be used.
 html_search_scorer = '_static/js/scorer.js'
 
 html_redirect_pages = redirects.REDIRECTS
@@ -201,13 +159,9 @@ html_redirect_pages = redirects.REDIRECTS
 # -- Options for LaTeX output ---------------------------------------------
 
 latex_elements = {
-    # Additional stuff for the LaTeX preamble.
     'preamble': r'\setcounter{tocdepth}{2}',
 }
 
-# Grouping the document tree into LaTeX files. List of tuples
-# (source start file, target name, title,
-#  author, documentclass [howto, manual, or own class]).
 latex_documents = [
   ('index', 'zephyr.tex', u'Zephyr Project Documentation',
    u'many', 'manual'),
@@ -226,10 +180,6 @@ breathe_domain_by_extension = {
 breathe_separate_member_pages = True
 breathe_show_enumvalue_initializer = True
 
-# Qualifiers to a function are causing Sphihx/Breathe to warn about
-# Error when parsing function declaration and more.  This is a list
-# of strings that the parser additionally should accept as
-# attributes.
 cpp_id_attributes = [
     '__syscall', '__deprecated', '__may_alias',
     '__used', '__unused', '__weak',