This one is actually quite simple after you find the first move. Black king is trapped on the side of the board, your king is close, so there is that mate pattern with your king opposite of his king, and your rook on the side of the board giving checkmate. There is also one other pattern: bishop (or Q) covering the corner, one other piece on or covering a specific square (g3 in this case) - preventing black king to get away, and rook giving the checkmate from the corner.
First move is 1.h3 Kxh3 and now I think it's 2.Kf4 to achieve those patterns I mentioned. Now if Kh4, then Rh1#. If Kh2, Rh1# too - white king is covering g3 square.
White to play and mate in three moves: