Gadgets are needed to comply with a protocol so which the interrupt-request (IRQ) traces is usually shared. The PCI bus features four interrupt lines, INTA# through INTD#, all of which can be found to every gadget. Nearly 8 PCI devices share the same IRQ line (INTINA# by way of INTINH#) https://nathanlabsadvisory.com/irs-efile/