Removing device driver code in mainboard.c for Tyan boards?

[YhLu]

chip northbridge/amd/amdk8                              
        device pci_domain 0 on                          
                device pci 18.0 on # LDT0       
.				....
			  End
			  ....
			  chip northbridge/amd/amdk8

				device pci 19.0 end
				...
			   End 
		End # PCI domain
.....acpic...
End # NB K8

It looks strang, 
Why not thang that to followings?

device pci_domain 0 on                          
	chip northbridge/amd/amdk8                              
                device pci 18.0 on # LDT0       
.				....
			  End
			  ....
	 End #NB K8
			  chip northbridge/amd/amdk8

				device pci 19.0 end
				...
			   End 
		End # PCI domain
.....apic....