Add methods for network segment range support

This patch introduces the ML2 type driver abstract methods
``initialize_network_segment_range_support`` and
``update_network_segment_range_allocations`` for the network segment
range support when the extension is loaded.

Co-authored-by: Allain Legacy <Allain.legacy@windriver.com>

Depends-on: https://review.openstack.org/624709
Partially-implements: blueprint network-segment-range-management
Change-Id: I825624b89530e13c326bffeb80fdd49f712a2399

neutron_lib/plugins/ml2/api.py

@@ -652,6 +652,26 @@ class ML2TypeDriver(_TypeDriverBase):
         """
         pass
 
+    @abc.abstractmethod
+    def initialize_network_segment_range_support(self):
+        """Perform driver network segment range initialization.
+
+        Called during the initialization of the ``network-segment-range``
+        service plugin if enabled, after all drivers have been loaded and the
+        database has been initialized. This reloads the `default`
+        network segment ranges when Neutron server starts/restarts.
+        """
+        pass
+
+    @abc.abstractmethod
+    def update_network_segment_range_allocations(self):
+        """Update driver network segment range allocations.
+
+        This syncs the driver segment allocations when network segment ranges
+        have been created, updated or deleted.
+        """
+        pass
+
 
 @six.add_metaclass(abc.ABCMeta)
 class NetworkContext(object):

releasenotes/notes/add-type-driver-methods-for-network-segment-range-e6d300d430d97dd6.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Introduce the ML2 type driver abstract methods
+    ``initialize_network_segment_range_support`` and
+    ``update_network_segment_range_allocations``
+    for the network segment range support when the extension is loaded.