The Internet of Things (IoT) is an emerging technology whose popularity and use cases grow with every passing day. Although the domain of IoT has proven to be transformative, as the deployment size of the network increases, it becomes a huge challenge to secure such a large number of heterogeneous devices connected by a complex network having a variety of access protocols. Software defined networking (SDN), with its unique capabilities of decoupling control plane from data plane and maintaining a centralized programmable controller, has been gaining a lot of prominence in solving the security challenges faced by the IoT domain. This work first analyzes the security threats faced by the IoT domain and the inherent architectural flaws for these vulnerabilities. It then goes on to understand how solutions presented by the modified architecture of SDN-IoT can help to tackle these challenges. Lastly, the work draws a realistic image of bringing in SDN-IoT by showcasing the critical issues faced by this domain and the current efforts attempting to solve these issues. Thus, it serves as a good primer for researchers looking to delve into the topic for tackling prevalent challenges.