All digital cameras are in "ir mode" point your TV remote at your cell phone camera and press a button on your remote it will light up on your screen.
My LG CX's remote uses IR for turning on, but beyond that it uses Bluetooth or some similar protocol.
Even if a remote is IR, rear cameras are often shielded against it. Front cameras, usually not. This is much easier to notice on IR-powered PC mice of course. Not sure if modern ones use IR as well - haven't checked.