doc: Add top-level navigation grid

Make the documentation page a little bit more interesting with top-level
navigation grid highlighting the most important sections with a brief
description.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/doc/index.rst b/doc/index.rst
index ad4b724..3ab1eda 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -16,13 +16,6 @@
    Welcome to the Zephyr Project's documentation. This is the documentation of the
    master tree under development (version |version|).
 
-   Documentation for tagged released versions of Zephyr can be found at
-   ``https://docs.zephyrproject.org/<version>``. The following documentation
-   versions are available:
-
-   `Zephyr 1.9.2`_ | `Zephyr 1.10.0`_ | `Zephyr 1.11.0`_ |
-   `Zephyr 1.12.0`_ | `Zephyr 1.13.0`_
-
 For information about the changes and additions for releases, please
 consult the published :ref:`zephyr_release_notes` documentation.
 
@@ -31,15 +24,76 @@
 imports or reuses packages, scripts, and other files that use other
 licensing, as described in :ref:`Zephyr_Licensing`.
 
-Source code for the Zephyr Project is maintained in the Zephyr Project's
-`GitHub repo`_.
-
 .. _Apache 2.0 license:
    https://github.com/zephyrproject-rtos/zephyr/blob/master/LICENSE
 
 .. _GitHub repo: https://github.com/zephyrproject-rtos/zephyr
 
 
+.. raw:: html
+
+   <ul class="grid">
+       <li class="grid-item">
+	   <a href="introduction/introducing_zephyr.html">
+	       <img alt="" src="_static/images/kite.png"/>
+	       <h2>Introduction</h2>
+	   </a>
+	   <p>Introducing the Zephyr Project: the overview, architecture, features and licensing</p>
+       </li>
+       <li class="grid-item">
+	   <a href="getting_started/getting_started.html">
+	       <img alt="" src=""/>
+	       <h2>Getting Started Guide</h2>
+	   </a>
+	   <p>Follow this guide to set up a Zephyr development environment on your
+	       system, and then build and run a sample application.</p>
+       </li>
+       <li class="grid-item">
+	   <a href="contribute/index.html">
+	       <img alt="" src=""/>
+	       <h2>Contribution Guidelines</h2>
+	   </a>
+	   <p>As an open-source project, we welcome and encourage the community
+           to submit patches directly to the project.</p>
+       </li>
+       <li class="grid-item">
+	   <a href="samples/samples.html">
+	       <img alt="" src=""/>
+	       <h2>Samples and Demos</h2>
+	   </a>
+	   <p>A list of samples and demos that can run on a variety of boards supported
+	       by Zephyr</p>
+       </li>
+       <li class="grid-item">
+	   <a href="kernel/kernel.html">
+	       <img alt="" src=""/>
+	       <h2>Kernel Services</h2>
+	   </a>
+	   <p>General introduction of the Zephyr kernel’s key capabilities and services.</p>
+       </li>
+       <li class="grid-item">
+	   <a href="security/security.html">
+	       <img alt="" src=""/>
+	       <h2>Security</h2>
+	   </a>
+	   <p>Requirements, processes, and developer guidelines for ensuring security is addressed within the Zephyr project.</p>
+       </li>
+       <li class="grid-item">
+	   <a href="boards/boards.html">
+	       <img alt="" src=""/>
+	       <h2>Supported Boards</h2>
+	   </a>
+	   <p>List if supported boards and platforms.</p>
+       </li>
+       <li class="grid-item">
+	   <a href="tools/index.html">
+	       <img alt="" src=""/>
+	       <h2>Tools</h2>
+	   </a>
+	   <p>List of Tools used for development.</p>
+       </li>
+   </ul>
+
 .. only:: html
 
    Sections