The following series of patches adds support for active-low gpio pins
as well as for systems with separate MDI and MDO pins to the mdio-gpio
driver.
A board using those features is based on a COM Express CPU board.
The COM Express standard supports GPIO pins on its connector,
with one caveat: The pins on the connector have fixed direction
and are hard configured either as input or output pins.
The COM Express Design Guide [1] provides additional details.
The hardware uses three of the GPO/GPI pins from the COM Express board
to drive an MDIO bus. Connectivity between GPI/GPO pins and the MDIO bus
is as follows.