The modernization of business processes have pressured Software-Intensive Information Systems (IS) to interoperate with several types of systems, such as cyberphysical systems, drones, satellites, and mobiles, arising a new type of complex systems so-called Systems-of-Information Systems (SoIS). Despite the novelty of the area as it has been known, it follows a trend of previous complex systems, such as Federated Information Systems and Large-Scale Information Systems. However, operational and managerial independence of IS constituents have created a new type of system that must be understood to suitably support new business and modernize old ones, such as pizza delivery via drone swarms. Hence, to sustain the area and achieve advances, it is necessary to externalize the state of the art and practice of the area. However, the lack of literature mappings on this topic can hamper the evolution of the area and pose difficulties to its progress, besides making it difficult to obtain relevant information about existing gaps and advances that could be made in the future. This paper presents results of a Systematic Mapping (SM) carried out to investigate the status quo of SoIS domain. We bring a panorama of this research topic and also indicate research perspectives. From a set of 212 studies, 25 were selected, analyzed and had their data extracted. Results reveal that interoperability between different IS is still a challenge and the low number of studies referring to languages, techniques and tools for modeling SoIS architectures points to an important area of study to be researched in the next years.