Gadgets are required to abide by a protocol so the interrupt-request (IRQ) lines is often shared. The PCI bus contains 4 interrupt traces, INTA# by means of INTD#, all of which can be found to every gadget. Nearly eight PCI units share exactly the same IRQ line (INTINA# by INTINH#) https://nathanlabsadvisory.com/iso-27001-information-security/