RC_INPUT module not available for fmuv2

The dev documentation mentions that there exists a RC_INPUT module for managing RC receiver input signals.
I have a cube pixhawk 2 which accepts firmware v2 but there is no RC_INPUT module available
I checked the fmuv5 and there exist RC_INPUT.
the question is how to accept msg from RC receiver? what is the Topic name?
or any doc for FMUv2.

another question is what is the module name responsible for it?

On fmu-v2/v3 the RC input comes from the px4io (a separate microcontroller). On fmuv5 the rc_input driver is available because the px4io is optional (pixhawk 4 vs 4 mini).