[coreboot] Kconfig defaults per chipset, or mainboard?

[Peter Stuge]

In src/Kconfig there is this:

config FALLBACK_VGA_BIOS_ID
        string "VGA BIOS ID"
        depends on VGA_BIOS
        default "1106,3230"
        help
          The ID that would associate your VGA BIOS to your video card.
          (PCI VendorID, PCI Device ID)

How does a component (nb, sb, sio) or mainboard provide an override
for this default?

//Peter