doc: convert internal http links to references

This converts the http links within the Zephyr document
into references. This allows the links within the PDF file
to jump to the correct sections instead of going to
the Internet.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

doc/contribute/contribute_guidelines.rst

@@ -48,10 +48,7 @@ Components using other Licenses
 ===============================
 
 There are some imported or reused components of the Zephyr project that
-use other licensing, as described in `Zephyr Licensing`_.
+use other licensing, as described in :ref:`Zephyr_Licensing`.
-
-.. _Zephyr Licensing:
-   https://docs.zephyrproject.org/LICENSING.html
 
 Importing code into the Zephyr OS from other projects that use a license
 other than the Apache 2.0 license needs to be fully understood in
@@ -62,11 +59,15 @@ By carefully reviewing potential contributions and also enforcing a
 the Zephyr community can develop products with the Zephyr Project
 without concerns over patent or copyright issues.
 
-See `Contributing non-Apache 2.0 components`_ for more information about
+See :ref:`contribute_non-Apache` for more information about
 this contributing and review process for imported components.
 
-.. _Contributing non-Apache 2.0 components:
+.. only:: latex
-   https://docs.zephyrproject.org/contribute/contribute_non-apache.html
+
+   .. toctree::
+      :maxdepth: 1
+
+      ../LICENSING.rst
 
 .. _DCO:
 
@@ -137,10 +138,7 @@ Prerequisites
 As a contributor, you'll want to be familiar with the Zephyr project, how to
 configure, install, and use it as explained in the `Zephyr Project website`_
 and how to set up your development environment as introduced in the Zephyr
-`Getting Started Guide`_.
+:ref:`getting_started`.
-
-.. _Getting Started Guide:
-   https://docs.zephyrproject.org/getting_started/getting_started.html
 
 You should be familiar with common developer tools such as Git and CMake, and
 platforms such as GitHub.
@@ -165,15 +163,12 @@ To clone the main Zephyr Project repository use::
 
     git clone https://github.com/zephyrproject-rtos/zephyr
 
-The Zephyr project directory structure is described in `Source Tree Structure`_
+The Zephyr project directory structure is described in :ref:`source_tree_v2`
 documentation. In addition to the Zephyr kernel itself, you'll also find the
 sources for technical documentation, sample code, supported board
 configurations, and a collection of subsystem tests.  All of these are
 available for developers to contribute to and enhance.
 
-.. _Source Tree Structure:
-   https://docs.zephyrproject.org/kernel/overview/source_tree.html
-
 Pull Requests and Issues
 ************************
 

samples/subsys/usb/webusb/README.rst

@@ -24,8 +24,7 @@ real usecase, implement applications based on the WebUSB API.
 Building and flashing
 *********************
 
-Refer to
+Refer to :ref:`arduino_101`
-https://www.zephyrproject.org/doc/boards/x86/arduino_101/doc/board.html
 for details on building and flashing the image into an Arduino 101.
 
 Testing with latest Google Chrome on host