Self-Organizing Network (SON) stands for a key concept characterizing the behavior of the future mobile networks. The evolution of telecom infrastructures towards 5G transforms the network management from the traditional and static processes to automatic and dynamic ones. SON was proposed to offer agile on-demand services to the users through providing self-adaptation capabilities to mobile networks on different categories. This paper presents a detailed and exhaustive survey on SON evolution from 4G towards 5G networks. The central focus of this survey is upon providing a deep understanding of SON mechanisms along with the architectural changes associated with 5G networks. Within this framework, the approaches and trends in self-organizing cellular networks are discussed. Additionally, the main functionalities of SON, namely self-configuration, self-optimization and self-healing are displayed. Our work serves as an enlightening guideline for future research works on SON as far as cellular networks domain is concerned.