In this paper, we propose to the concept of software-defined networking (SDN) in wireless sensor networks (WSNs) with a structured and hierarchical management. We argue that structured and hierarchical management using SDN promises a solution to some inherent problems in WSN management. Furthermore, we propose a cluster based architecture with multiple base stations as hosts for the SDN control functions and as cluster heads in the same time. We also suggest a general architecture for a software-defined wireless sensor network where the controller exchanges information with other SDN domains. We call this new architecture: software-defined clustered sensor networks (SDCSN). In addition we highlight some future directions and raise some important questions that need to be investigated in future research in software-defined networks for ad-hoc and sensor networks.