Adding Release and version management for L2GW package

This patch describes the philopsphy of release and version
management for L2 Gateway package. This also specifies the
use case example for this package for specific release.

Change-Id: I721a6c277ffc835cf51c6c08aace6fd388ba97f1

doc/source/usage.rst

@@ -78,4 +78,75 @@ L2 Gateway Agent connects to ovsdb server to configure and fetch L2 Gateways
            :width:  450px
            :align: center
 
+.. _l2gw_release_management
+
+6. L2GW Package Versioning and Release Management
+=================================================
+
+Versioning of L2 Gateway Package
+--------------------------------
+L2 Gateway package will be uploaded, as networking-l2gw,
+to https://pypi.python.org.
+In order to upload this package, it will be versioned.
+Any subsequent updates will require version updates.
+This sub-section describes the versioning and release management of this package.
+
+By keeping L2 Gateway repository out of Neutron main repository gives us
+flexibility in terms of development and enhancements.
+This flexibility is extended for versioning of this project as well - this
+means, if we wanted to, we could version this project sequentially.
+This means whenever a new fix is released, we could bump up the version to
+the next number.
+
+Flexibility comes with cost. Thinking in terms of future, assuming this API
+is deployed by many users along with different releases of Neutron.
+Many enhancements/fixes may be introduced to this project.
+If we incremented the version/release number sequentially, this may force
+uninterested users to upgrade as well.
+This may or may not be desirable. Therefore, following release/versioning
+proposal is suggested for this package.
+
+Versioning of L2 Gateway will be aligned closely with Neutron releases.
+Neutron releases are formatted as follows::
+
+       <year>.<major-release>.<minor-release>
+
+       year = 2015, 2014, etc...
+       major-release = 1 or 2  - only two releases in a year
+       minor-release = 1,2,3 or b1,b2,b3, or rc1,rc2,rc3, etc
+
+       2015.1.1, 2014.2.rc2, etc…
+
+L2 Gateway package is versioned in the same manner with an exception that the
+last tuple is used for intermediate patches/fixes between major release.
+As an example, the first release will be::
+
+       2015.1.X   where X will continue to increment as we add fixes to this release
+
+When kilo is released, L2 Gateway repository will also be tagged as kilo/stable
+to match with Neutron release.
+At this time the version of this package will be tagged to
+2015.1.X ("X" will continue to increase as bug fixes are added to kilo/stable).
+For liberty release, the version of this package will be changed to 2015.2.Y.
+All the new features will be added to 2015.2.Y and all the bug fixes for kilo
+will be back-ported to 2015.1.X.
+This gives the flexibility of keeping the contents/features of this package
+closely aligned with Neutron releases.
+
+Which Version of L2 Gateway Package to use?
+-------------------------------------------
+
+Anybody who wants to use L2 Gateway package, they can install it by issuing::
+
+       pip install networking-l2gw
+
+This will always pick the latest version of the package.
+However, for those users who are already using this package and want to pick
+up point fixes for a given release may use the specific version.
+For example, if a user wants to pick the latest version of the package that is
+suitable for kilo/stable, may use the following::
+
+       pip install networking-l2gw>=2015.1.X,<2015.2.0
+
+
 For information on deploying L2GW refer networking-l2gw/doc/source/installation.rst  and  in devstack , networking-l2gw/devstack/README.rst