Topic: Routing requests to Service provider.
First, we need to understand different RPC Service Types, that MD-SAL supports. For a southbound plugin, we use Routed Service.
Second, we need to understand that SalFlowService is a RpcService that provides APIs to add, delete and update flows.
Third, BindingAwareBroker provides an interface RoutedRpcRegistration that provides API to register particular instance identifier to be processed by a given RpcService.