I asked beforehand about imx6q's ability to use RGMII & MII peripheries in the same time (Can these peripheries be active in the same time)?
answer: IMX6Q has ENET module, which supports MII, RMII, RGMII interfaces Pins affected are described in Table 23-1 (ENET External Signals) of the i.MX6 RM (Rev. 3, 07/2015). Only single interface may be used at a time because of multiplexing.
what is the origin of multiplexing? is it pin mux or other kind?