We discuss a design methodology for SegBus, a multicore segmented bus platform. The methodology supports the modeling of the platform at several abstraction levels, enabling the designer to focus only on the relevant aspects of the architecture at a given development stage. We employ the Unified Modeling Language (UML) as a specification language for the SegBus platform and we customize its elements to serve our specific purposes via the profiling mechanism. The approach enables us to take advantage of graphical models of the platform and of automated refinements of these models towards implementation.