The Internet of Things (IoT) paradigm is growing, affecting human life and aiming to solve problems in the real world, i.e., in education, healthcare, smart homes, intelligent transportation, and other areas. However, it is a fact that the development of IoT systems is complicated compared to that of traditional software systems, especially in relation to requirements engineering (RE). The RE of IoT systems is not implemented frequently due to their broad aspects, such as the variety of user needs, making these systems difficult to construct. In this sense, the use of loT-based systems has not been well explored by the research community in order to provide well-planned proposals to improve the quality of their performance. In this work, we present a comprehensive and inclusive review of the RE of loT-based systems. To accomplish this, a systematic mapping study (SMS) is presented to evaluate the use of parameters based on the existing literature. SMS is a methodology used for research in the medical field and has recently been implemented in software engineering (SE) to sort and organize research publications to gain knowledge on progress and identify research gaps. In this article, we aim to classify the existing research publications in the current scientific literature regarding RE proposals for IoT software systems and review their implications for future research. This will make it possible to establish lines of research in order to improve the quality of the development of future IoT systems.