  We consider a port-Hamiltonian system on a spatial domain $\Omega \subseteq
\mathbb{R}^n$ that is bounded with Lipschitz boundary. We show that there is a
boundary triple associated to this system. Hence, we can characterize all
boundary conditions that provide unique solutions that are non-increasing in
the Hamiltonian. As a by-product we develop the theory of quasi Gelfand
triples. Adding ``natural'' boundary controls and boundary observations yields
scattering/impedance passive boundary control systems. This framework can be
applied to the wave equation, Maxwell equations and Mindlin plate model, and
probably many more.
