APIC Descriptor Table to enumerate both I/O APICs and local APICs. ACPI
does not embed PCI interrupt routing information in the MADT like the MP
Table does. Instead, ACPI stores the PCI interrupt routing information
in the _PRT object under each PCI bus device. The MADT table simply
provides hints about which interrupt vectors map to which I/O APICs. Thus
when using ACPI, the existing ACPI PCI bridge drivers are sufficient to
route PCI interrupts.
