Merge branch 'FEC-MDIO-speedups'

Andrew Lunn says:

====================
FEC MDIO speedups

This patchset gives a number of speedups for MDIO with the FEC.
Replacing interrupt driven with polled IO brings a big speedup due to
the overheads of interrupts compared to the short time interval.
Clocking the bus faster, when the MDIO targets supports it, can double
the transfer rate. And suppressing the preamble, if devices support
it, makes each transaction faster.

By default the MDIO clock remains 2.5MHz and preables are used. But
these can now be controlled from the device tree. Since these are
generic properties applicable to more than just FEC, these have been
added to the generic MDIO binding documentation.

v2:
readl_poll_timeout()
Add patches to set bus frequency and preamble disable

v3:
Add Reviewed tags
uS->us
readl_poll_timeout_atomic()
Extend DT binding documentation
====================

Acked-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>