There are a number of different PHYs accounted for by the broadcom driver. To decide which initialization routine to call, MMIO offset 0x3E0 is checked to verify the PHY type and the PHY Revision. More information is available on PHYVersioning
There is a dummy read from MMIO offset 0x120 before an initialization routine is selected.
A PHYs (PHY Type 0)
B PHYs (PHY Type 1)
B2PHY - B PHYs with PHY Revision 2
B4PHY - B PHYs with PHY Revision 4
B5PHY - B PHYs with PHY Revision 5
B6PHY - B PHYs with PHY Revision 6
G PHYs (PHY Type 2)