Rock3A full uart cts/rts

I have a problem, I have to use 3 uart serials on Rock 3A, and so far everything works.
Now my problem arises when I have to connect to serial lines and also use flowcontrol rts/cts, I know they are not used much anymore, but in this case to communicate with other specific devices, I have to do it.
if I use mraa-uart I can activate the flowcontrol, but how do I know the cts and rts pins of uart0, uart2, uart3?

Thanks to anyone with information