In this paper we present ongoing work towards a programming framework for heterogeneous hardware- and software environments. Our framework aims at improving programmability and portability for heterogeneous many-core systems via a Platform Description Language (PDL) for expressing architectural patterns and platform information. We developed a prototypical code generator that takes as input an annotated serial task-based program and outputs, parametrized via PDL descriptors, code for a specific target heterogeneous computing system. By varying the target PDL descriptor, code for different target configurations can be generated without the need to modify the input program. We utilize a simple task-based programming model for demonstration of our approach and present preliminary results indicating its applicability on a state-of-the-art heterogeneous system.