docs: infiniband: convert docs to ReST and rename to *.rst

The InfiniBand docs are plain text with no markups.  So, all we needed to
do were to add the title markups and some markup sequences in order to
properly parse tables, lists and literal blocks.

At its new index.rst, let's add a :orphan: while this is not linked to the
main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/Documentation/infiniband/index.rst b/Documentation/infiniband/index.rst
new file mode 100644
index 0000000..22eea64
--- /dev/null
+++ b/Documentation/infiniband/index.rst
@@ -0,0 +1,23 @@
+:orphan:
+
+==========
+InfiniBand
+==========
+
+.. toctree::
+   :maxdepth: 1
+
+   core_locking
+   ipoib
+   opa_vnic
+   sysfs
+   tag_matching
+   user_mad
+   user_verbs
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`