Add release notes for Cyborg-Nova integration.

Change-Id: I4b630d755f99863faf6a432b086608d494ef3cc3
Blueprint: nova-cyborg-interaction

api-guide/source/accelerator-support.rst

@@ -0,0 +1,56 @@
+==============================
+Using accelerators with Cyborg
+==============================
+
+Starting from microversion 2.82, nova supports creating servers with
+accelerators provisioned with the Cyborg service, which provides lifecycle
+management for accelerators.
+
+To launch servers with accelerators, the administrator (or an user with
+appropriate privileges) must do the following:
+
+  * Create a device profile in Cyborg, which specifies what accelerator
+    resources need to be provisioned. (See `Cyborg device profiles API
+    <https://docs.openstack.org/api-ref/accelerator/v2/index.html#device-profiles>`_.
+
+  * Set the device profile name as an extra spec in a chosen flavor,
+    with this syntax:
+
+    .. code::
+
+       accel:device_profile=$device_profile_name
+
+   The chosen flavor may be a newly created one or an existing one.
+
+  * Use that flavor to create a server:
+
+    .. code::
+
+       openstack server create --flavor $myflavor --image $myimage $servername
+
+As of 21.0.0 (Ussuri), nova supports only specific operations for instances
+with accelerators. The lists of supported and unsupported operations are as
+below:
+
+  * Supported operations.
+
+    * Creation and deletion.
+    * Reboots (soft and hard).
+    * Pause and unpause.
+    * Stop and start.
+    * Take a snapshot.
+    * Backup.
+    * Rescue and unrescue.
+
+  * Unsupported operations
+
+    * Rebuild.
+    * Resize.
+    * Evacuate.
+    * Suspend and resume.
+    * Shelve and unshelve.
+    * Cold migration.
+    * Live migration.
+
+Some operations, such as lock and unlock, work as they are effectively
+no-ops for accelerators.

api-guide/source/index.rst

@@ -88,3 +88,4 @@ Contents
     request_and_response_formats
     down_cells
     port_with_resource_request
+    accelerator-support

releasenotes/notes/accelerator-requests-6c9a6fef77ab776a.yaml

@@ -4,7 +4,11 @@ features:
     Handling accelerator requests for an instance is now supported (where
     supported by the underlying virt driver) as of microversion
     2.82. The Cyborg service generates an event for the binding
-    completion for each accelerator request for an instance.
+    completion for each accelerator request (ARQ) for an instance.
-    Adds a new event ``accelerator_request_bound`` for this to the API:
+    Adds a new event ``accelerator_request_bound`` for this to the API
+    ``POST /os-server-external-events``
 
-    * ``POST /os-server-external-events``
+    The lists of operations that are supported or unsupported for
+    instances with accelerators are listed in
+    `accelerator operation guide
+    <https://docs.openstack.org/api-guide/compute/accelerator-support.html>`_