Move supported messaging drivers in-tree

Up until now it has only been available in the OpenStack spec, but it is
a living document and I believe we can maintain it in oslo.messaging's
tree.

Change-Id: I7bb9e5f02004f857d8f75909fcc0d05f2882a77d

doc/source/index.rst

@@ -23,6 +23,7 @@ Contents
    opts
    conffixture
    drivers
+   supported-messaging-drivers
    AMQP1.0
    zmq_driver
    FAQ

doc/source/supported-messaging-drivers.rst

@@ -0,0 +1,60 @@
+=============================
+ Supported Messaging Drivers
+=============================
+
+RabbitMQ may not be sufficient for the entire community as the community
+grows. Pluggability is still something we should maintain, but we should
+have a very high standard for drivers that are shipped and documented
+as being supported.
+
+This document defines a very clear policy as to the requirements
+for drivers to be carried in oslo.messaging and thus supported by the
+OpenStack community as a whole. We will deprecate any drivers that do not
+meet the requirements, and announce said deprecations in any appropriate
+channels to give users time to signal their needs. Deprecation will last
+for two release cycles before removing the code. We will also review and
+update documentation to annotate which drivers are supported and which
+are deprecated given these policies
+
+Policy
+------
+
+Testing
+~~~~~~~
+
+* Must have unit and/or functional test coverage of at least 60% as
+  reported by coverage report. Unit tests must be run for all versions
+  of python oslo.messaging currently gates on.
+
+* Must have integration testing including at least 3 popular oslo.messaging
+  dependents, preferrably at the minimum a devstack-gate job with Nova,
+  Cinder, and Neutron.
+
+* All testing above must be voting in the gate of oslo.messaging.
+
+Documentation
+~~~~~~~~~~~~~
+
+* Must have a reasonable amount of documentation including documentation
+  in the official OpenStack deployment guide.
+
+Support
+~~~~~~~
+
+* Must have at least two individuals from the community commited to
+  triaging and fixing bugs, and responding to test failures in a timely
+  manner.
+
+Prospective Drivers
+~~~~~~~~~~~~~~~~~~~
+
+* Drivers that intend to meet the requirements above, but that do not yet
+  meet them will be given one full release cycle, or 6 months, whichever
+  is longer, to comply before being marked for deprecation. Their use,
+  however, will not be supported by the community. This will prevent a
+  chicken and egg problem for new drivers.
+
+.. note::
+
+  This work is licensed under a Creative Commons Attribution 3.0 Unported License.
+  http://creativecommons.org/licenses/by/3.0/legalcode