Merge branch 'net-ethernet-dwmac-add-ethernet-glue-logic-for-NXP-imx8-chip'

Fugang Duan says:

====================
net: ethernet: dwmac: add ethernet glue logic for NXP imx8 chip

NXP imx8 family like imx8mp/imx8dxl chips support Synopsys
MAC 5.10a IP, the patch set is to add ethernet DWMAC glue
layer including clocks, dwmac address width, phy interface
mode selection and rgmii txclk rate adjustment in runtime.

v1 -> v2:
- suggested by Andrew: add the "snps,dwmac-5.10a" compatible
  string into NXP binding documentation.
- suggested by David: adjust code sequences in order to have
  reverse christmas tree local variable ordering.

Thanks Andrew and David for the review.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>