phy_start_machine — start PHY state machine tracking
the phy_device struct
callback function for state change notifications
The PHY infrastructure can run a state machine which tracks whether the PHY is starting up, negotiating, etc. This function starts the timer which tracks the state of the PHY. If you want to be notified when the state changes, pass in the callback handler, otherwise, pass NULL. If you want to maintain your own state machine, do not call this function.