doc:process: add links where missing

Some documents are refering to others without links. With this
patch I add those missing links.

This patch affects only documents under process/ and labels where
necessary.

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/doc-guide/sphinx.rst b/Documentation/doc-guide/sphinx.rst
index f0796da..02605ee 100644
--- a/Documentation/doc-guide/sphinx.rst
+++ b/Documentation/doc-guide/sphinx.rst
@@ -1,3 +1,5 @@
+.. _sphinxdoc:
+
 Introduction
 ============