ONOS-7739 Support for P4Runtime multicast programming

Design doc: https://docs.google.com/document/d/13rkQlwr49M-uxQQEuxCMP7BFEPY2gtQ850Hn3gUfesU/edit#heading=h.lzdayib259sq

Change-Id: Ief00bec89fe5a9784b0ee13fdaafa3ae58ab654f
diff --git a/core/api/src/main/java/org/onosproject/net/pi/service/PiMulticastGroupTranslationStore.java b/core/api/src/main/java/org/onosproject/net/pi/service/PiMulticastGroupTranslationStore.java
new file mode 100644
index 0000000..f961d84
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/pi/service/PiMulticastGroupTranslationStore.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.net.pi.service;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.net.group.Group;
+import org.onosproject.net.pi.runtime.PiMulticastGroupEntry;
+
+/**
+ * A PI translation store that keeps track of which groups have been
+ * translated to which PI PRE multicast groups.
+ */
+@Beta
+public interface PiMulticastGroupTranslationStore
+        extends PiTranslationStore<Group, PiMulticastGroupEntry> {
+}