raise-frame is an interactive built-in function in ‘C source code’.
(raise-frame &optional FRAME)
Bring FRAME to the front, so it occludes any frames it overlaps.
If FRAME is invisible or iconified, make it visible.
If you don’t specify a frame, the selected frame is used.
If Emacs is displaying on an ordinary terminal or some other device which
doesn’t support multiple overlapping frames, this function selects FRAME.