How can the STM32H7 communicate with a Clause 45 PHY?

[nrg6]

Can somebody give an example or pseudocode how to use the Ethernet MAC with a Clause 45 PHY? What is the correct setting for MACMDIOAR register to use Clause 45? Unfortunately, the RM doesn't say a lot.

I used the functions HAL_ETH_WritePHYRegister() and HAL_ETH_ReadPHYRegister() successfully with a Clause 22 PHY, but they don't work for Clause 45.