For devices that aren't specified as compatible with Control Center, those devices can be controlled by CEC thru the HDMI cable or by IR. If the device doesn't use IR, then Control Center will attempt to communicate basic functions with CEC. If it is not able to control the device, you can still control it with the original device remote that came with your device.
Control Center can still make your source switching easy, after which you can use the original remote to control your device.
Please see our article about Compatible Devices.
