Devices are necessary to follow a protocol so the interrupt-ask for (IRQ) lines is usually shared. The PCI bus involves 4 interrupt lines, INTA# by means of INTD#, all of which are available to every system. Around 8 PCI equipment share the exact same IRQ line (INTINA# by INTINH#) in https://nathanlabsadvisory.com/nist-800-cyber-security-frame-work/