RS485

Hi
I’m trying get working rs485 on beaglebone black. I have tryed with out success the BB-UART4-RS485 overlay with kernel 4.4
Are the lastest images capable with the 8250 driver or must use OMAP driver?
I have build kernel 3.8.13-bone86 with Omap but when loading the BB-UART4-RS485, /dev/ttyO3 is created instead of /dev/ttyO4.

Any help is welcome.
Thanks