Discrete mathematics is simply too diverse for there to be a single named branch of mathematics that combines it with linear algebra. (See the Wikipedia article to get an impression of discrete mathematics' breadth.)
That said, when it comes to subfields, graph theory is a major subarea under the umbrella of discrete mathematics and algebraic graph theory draws heavily on both linear algebra and group theory. (See, for instance, Algebraic Graph Theory by Godsil and Royle.)
As mentioned in luegofuego's answer, the subfield of algebraic combinatorics uses concepts and techniques from abstract algebra and linear algebra. For matroid theory in particular, you might want to take a look at Matroids: A Geometric Introduction by Gordon and McNulty.
If you extend the umbrella far enough, you can include linear programming/optimization, which certainly uses linear algebra, but does not include algebraic in the name of the field, although the adjective linear does appear.