Auto-Negociation fails between two Ethernet Marvell PHYs (88E1111)

Have a look at the Triple Speed Ethernet user manual, there is a register range that can be used to access the MDIO registers.

You will need to tap into the driver, to access those registers after the PHY has been properly detected. The easiest is probably to go into the Marvel specific code and configure the registers there.

The 88E1111 datasheet isn't publicly available, unfortunately, but the MDIO registers 0-7 are standard, so you can pick the datasheet of any other PHY chip to get a description of those registers.