The Driver Family Override Protocol is an optional feature for UEFI Drivers following the UEFI Driver Model. The Driver Family Override Protocol provides a method for a UEFI Driver to opt-in to a higher priority rule for connecting drivers to controllers in the EFI Boot Service
ConnectController(). This rule is higher priority than the Bus Specific Driver Override Protocol rule and lower priority than the Platform Driver Override Rule.
The Driver Family Override Protocol is typically produced by UEFI Drivers associated with a family of similar controllers when multiple versions of a UEFI Driver for a family of similar controllers are present in a platform at the same time and where the UEFI Driver writer requires that the UEFI Driver considered the highest version manage all controllers in that same family.
PCI Use Case: If a platform has 3 PCI SCSI adapters from the same manufacturer, and the manufacturer requires the PCI SCSI adapter that has the highest version UEFI Driver to manage all 3 PCI SCSI adapters, then the Driver Family Override Protocol is required and it provides the version value used to make the selection. If the Driver Family Override Protocol is not produced, then the Bus Specific Driver Override Protocol for PCI selects the UEFI Driver from the PCI Option ROM to the adapter to manage each adapter.