  In this paper we study a subordinate Brownian motion with a Gaussian
component and a rather general discontinuous part. The assumption on the
subordinator is that its Laplace exponent is a complete Bernstein function with
a L\'evy density satisfying a certain growth condition near zero. The main
result is a boundary Harnack principle with explicit boundary decay rate for
non-negative harmonic functions of the process in $C^{1,1}$ open sets. As a
consequence of the boundary Harnack principle, we establish sharp two-sided
estimates on the Green function of the subordinate Brownian motion in any
bounded $C^{1,1}$ open set $D$ and identify the Martin boundary of $D$ with
respect to the subordinate Brownian motion with the Euclidean boundary.
