doc: Edit the heading markup

Edited heading markup for consistancy.

Change-Id: Ic91cea28427be92e82f1318821a6eead78467c52
Signed-off-by: Aceves <gerardo.aceves@intel.com>

doc/collaboration/documentation/code_blocks.rst

@@ -1,7 +1,7 @@
 .. _code_examples:
 
 Code Examples
-*************
+#############
 
 Collaborating to the Zephyr Kernel is all about code. Therefore, your
 documentation must include code examples. The code examples can be
@@ -22,7 +22,7 @@ Use these guidelines to insert code blocks to your documentation:
 * Treat all console commands that a user must use as code examples.
 
 Examples
---------
+********
 
 This is a code example included from a file in another directory. Only
 certain lines of the source file are included. Those lines of code are
@@ -120,7 +120,7 @@ Renders as:
 
 
 Templates
----------
+*********
 
 We have included templates for a basic ``.. code-block::`` directive
 and for a ``.. literalinclude::`` directive.

doc/collaboration/documentation/cross.rst

@@ -1,7 +1,7 @@
 .. _cross:
 
 Cross References
-****************
+################
 
 Sphinx and ReST provide different methods to create both internal and
 external cross references. Use only the following methods to increase the
@@ -10,7 +10,7 @@ consistency of the documents.
 .. _internal_cross:
 
 Internal Cross References
-=========================
+*************************
 
 An internal cross reference is a reference to a location within the Zephyr Project's
 documentation. Use explicit markup labels and the ``:ref:`` markup to
@@ -62,8 +62,8 @@ Use the following templates to insert internal cross references properly.
 
    .. _label_of_target:
 
-   This Is a Heading
-   -----------------
+   This Is a Level Three Heading
+   =============================
 
    This creates a link to the :ref:`label_of_target` using the text of the
    heading.
@@ -75,8 +75,8 @@ The template renders as:
 
 .. _label_of_target:
 
-This Is a Heading
------------------
+This Is a Level Three Heading
+=============================
 
 This creates a link to the :ref:`label_of_target` using the text of the
 heading.
@@ -91,7 +91,7 @@ This creates a link to the :ref:`target <label_of_target>` using the word
    Sphinx builders that support cross references.
 
 Referencing In-code Documentation
-=================================
+*********************************
 
 We have integrated in-code documentation using Sphinx and :program:`Breath`.
 This integration allows us to cross reference functions, variables, macros
@@ -114,7 +114,7 @@ reference to a documented code element.
    documented in the code following the :ref:`code`.
 
 External References
-===================
+*******************
 
 External references or hyperlinks can be added easily with ReST. The allowed
 methods are explicit hyperlinks and hyperlinks with a separated target

doc/collaboration/documentation/images.rst

@@ -1,7 +1,7 @@
 .. _images:
 
 Images
-******
+######
 
 Images grab the reader's attention and convey information that
 sometimes is difficult to explain using words alone. Well-planned
@@ -46,7 +46,7 @@ Follow these guidelines when creating graphics for the Zephyr Project:
   fibers.svg` or :file:`nanokernel_fiber-1.png`.
 
 Examples
-========
+********
 
 These examples follow the guidelines and can be used used as reference.
 
@@ -77,7 +77,7 @@ and linked to make identifying them easier.
    This screenshot shows a code comparison.
 
 Templates
-=========
+*********
 
 Use this template to add a figure to your documentation according to
 these guidelines.

doc/collaboration/documentation/inline.rst

@@ -1,7 +1,7 @@
 .. _inline:
 
 Inline Markup
-*************
+#############
 
 Sphinx supports a large number of inline markup elements. The
 documentation of the Zephyr OS only requires the use of the inline

doc/collaboration/documentation/tables.rst

@@ -1,7 +1,7 @@
 .. _rest_tables:
 
 Tables
-******
+######
 
 Tables must only be used for information that is either too numerous or too
 related for a list to be appropriate. The general rule of thumb is that the