doc: Convert internal links to RST format

Currently links between documents are using the format:

<path/to/><filename>.rst

This was required for services like GitHub because they render each
document in isolation - linking to another document is like linking
to any other file, just provide the full path.

However, with the new approach, the .rst files are only the raw
source for the documents. Once the documents have been rendered
the output is now in another format (HTML in our case) and so,
when linking to another document, the link must point to the
rendered version and not the .rst file.

The RST spec provides a few methods for linking between content.
The parent of this patch enabled the automatic creation of anchors
for document titles - we will use these anchors as the targets for
our links. Additional anchors can be added by hand if needed, on
section and sub-section titles, for example.

An example of this new format, for a document with the title
"Firmware Design" is :ref:`Firmware Design`.

One big advantage of this is that anchors are not dependent on
paths. We can then move documents around, even between directories,
without breaking any links between documents. Links will need to be
updated only if the title of a document changes.

Change-Id: I9e2340a61dd424cbd8fd1ecc2dc166f460d81703
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/components/platform-interrupt-controller-API.rst b/docs/components/platform-interrupt-controller-API.rst
index 7890cd3..9d02f45 100644
--- a/docs/components/platform-interrupt-controller-API.rst
+++ b/docs/components/platform-interrupt-controller-API.rst
@@ -3,9 +3,8 @@
 
 This document lists the optional platform interrupt controller API that
 abstracts the runtime configuration and control of interrupt controller from the
-generic code. The mandatory APIs are described in the `porting guide`__.
-
-.. __: ../getting_started/porting-guide.rst#interrupt-management-framework-in-bl31
+generic code. The mandatory APIs are described in the
+:ref:`Porting Guide <porting_guide_imf_in_bl31>`.
 
 Function: unsigned int plat_ic_get_running_priority(void); [optional]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -303,6 +302,6 @@
 In case of Arm standard platforms using GIC, the implementation of the API
 masks out the interrupt ID field from the acknowledged value from GIC.
 
-----
+--------------
 
-*Copyright (c) 2017-2018, Arm Limited and Contributors. All rights reserved.*
+*Copyright (c) 2017-2019, Arm Limited and Contributors. All rights reserved.*