Add SIG status tag reference

Change-Id: If2a39180734d20e1c954576476a4b8330e4f31ec

completed-sigs.yaml

@@ -0,0 +1,16 @@
+Upgrade:
+  chairs:
+    - name: James Page
+      irc: jamespage
+      email: james.page@canonical.com
+    - name: Lujin Luo
+      irc: lujinluo
+      email: luo.lujin@jp.fujitsu.com
+  scope: >
+    The objective of the Upgrade SIG is to improve the overall upgrade
+    process for OpenStack Clouds, covering both offline 'fast-forward'
+    upgrades and online 'rolling' upgrades, by providing a forum for
+    cross-project collaboration between operators and developers to
+    document and codify best practice for upgrading OpenStack.
+  status: completed
+  url: https://wiki.openstack.org/wiki/Upgrade_SIG

doc/source/index.rst

@@ -63,3 +63,8 @@ questions, please ask them on the `openstack-discuss mailing-list`_
 with subject prefix ``[meta-sig]``.
 
 .. _`openstack-discuss mailing-list`: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-discuss
+
+.. toctree::
+   :maxdepth: 1
+
+   reference/sig-status

doc/source/reference/sig-status.rst

@@ -0,0 +1,44 @@
+==========
+SIG status
+==========
+
+SIGs can be tagged with different status and let people understand the SIG's
+purpose and current state. You can find current status of each SIG under
+`SIG Governance`_. Here are valid statuses:
+
+active
+-------
+
+The SIG reaches out for discussion, have plans for current
+cycle, host meetings or send messages about status out to the mailing-list
+regularly.
+
+forming
+-------
+
+The SIG is still setting up. This status also applied to SIG which needs to
+regroup.
+
+advisory
+--------
+
+The SIG is not actively meeting or driving specific goals every cycle. SIG
+members stay around for help, make sure everything stays working and
+provide advice when needed.
+
+complete
+--------
+
+The SIG completed its mission and moved to `Completed SIGs`_.
+Completed SIGs can own repositories if required. But those should be marked as
+unmaintained.
+
+backlog
+-------
+
+The SIG didn't complete its mission and moved to backlog-sigs since this SIG
+can't maintain itself and can't find anyone to run the chair. Backlog SIGs can
+own repositories if required. But those should be mark as unmaintained.
+
+.. _SIG Governance: https://opendev.org/openstack/governance-sigs/src/branch/master/sigs.yaml
+.. _Completed SIGs: https://opendev.org/openstack/governance-sigs/src/branch/master/completed-sigs.yaml