-Energy efficiency is one of the key requirements in Wireless Sensor Networks (WSNs). In order to optimize energy usage at sensor nodes, this paper proposes a new network architecture that relies on concepts of Software Defined Networking (SDN). Since SDN is a relatively new technology, originally envisioned for wired networks, it cannot be expected to get immediately and completely adopted in WSN domain, regardless of potential benefits. For this reason, we consider incremental SDN deployment where SDN nodes coexist with traditional sensor nodes, and propose a new routing algorithm for SDN controller that prolongs the WSN lifetime even when a small percentage of SDN nodes is deployed.