The idea of leveraging Software Defined Networking (SDN) in vehicular networks has drawn a lot of attention in the last years. SDN flexibility and programmability brought promising solutions for VANET challenges, namely Quality of Services (QoS) and scalability which are the main characteristics of Internet of Vehicles (IoV). Such networks are characterized by fast topological changes due to their variable dynamicity and density. In fact, SDN decouples control plane and data plane, providing programmability to configure the network. However, based on a single controller, SDN is criticized for not supporting scalability and for decreasing the overall network Quality of service. Using multiple controllers becomes the tendency of recent works to meet the need of large networks. Throughout this paper, we survey the proposed SDN-based architectures for vehicular networks. Considering the control plane impact, centralized or distributed, the QoS improvements brought by theses architectures are studied and criticized in order to derive the suitability of each proposal to resolve the IoV challenges and meet its requirements for the various applications.