My sister has a doggie door in the laundry room into the garage. The doggie door opens near the wall, under a work table that is fenced in so the cat just has space there for the cat box and turning around. It keeps the smells well out of the house, and the cat from mischief in the garage. I think they used a child gate across the front. My laundry room isn't next to a corner of the garage so I couldn't set it up like that.
good luck