Here are the upcoming Raspberry Pi specific features for Mainline Linux 5.8:
- proper USB support for Raspberry Pi 4 boards without separate VL805 EEPROM
I don't know the details, but the VideoCore cares about the VL805 and it's firmware. The kernel only needs to notify the VC about XHCI resets, because after a reset the RAM of the VL805 is cleared and the firmware lost. This is very hacky.