[ONOS-6688] Add Permission message type in protobuf model

Change-Id: Iaad4783eba0a5d318c7b8a458c44a857f393b220
diff --git a/incubator/protobuf/models/src/main/proto/security/PermissionProto.proto b/incubator/protobuf/models/src/main/proto/security/PermissionProto.proto
new file mode 100644
index 0000000..24272cb
--- /dev/null
+++ b/incubator/protobuf/models/src/main/proto/security/PermissionProto.proto
@@ -0,0 +1,11 @@
+syntax = "proto3";
+option java_package = "org.onosproject.grpc.security.models";
+
+package security;
+
+// Corresponds to org.onosproject.security.Permission.
+message PermissionProto {
+    string classname = 1;
+    string name = 2;
+    string actions = 3;
+}