I have been struggling with RMII support on the IMX6D. We have a custom board using the KSZ8061. I've modifies the device tree to reflect the connection on the circuit board but I've already spent a week trying to get the PHY to work to no avail. I've also used the MX6_enet_RMII reference from Duan Fugan from NXP (https://community.nxp.com/t5/i-MX-Processors/iMX6-RGMII-ENET-REF-CLK-ENET-TX-CLK/m-p/265803). I can forward the path that we made for u-boot to try and get the RMII interface working. We would like to get assistance on getting this working.