added more mastership-related interfaces

Change-Id: I3c5da1e2a4346d6e557232c5f896b32a7268ec39
diff --git a/core/api/src/main/java/org/onlab/onos/cluster/MastershipAdminService.java b/core/api/src/main/java/org/onlab/onos/cluster/MastershipAdminService.java
new file mode 100644
index 0000000..6c58020
--- /dev/null
+++ b/core/api/src/main/java/org/onlab/onos/cluster/MastershipAdminService.java
@@ -0,0 +1,20 @@
+package org.onlab.onos.cluster;
+
+import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.MastershipRole;
+
+/**
+ * Service for administering the inventory of device masterships.
+ */
+public interface MastershipAdminService {
+
+    /**
+     * Applies the current mastership role for the specified device.
+     *
+     * @param instance controller instance identifier
+     * @param deviceId device identifier
+     * @param role     requested role
+     */
+    void setRole(InstanceId instance, DeviceId deviceId, MastershipRole role);
+
+}