All interrupt handlers perform the same four basic actions:
1. Save the IRQ value and the registers contents in the Kernel Mode stack.
2. Send an acknowledgment to the PIC that is servicing the IRQ line, thus allowing it to
issue further interrupts.
3. Execute the interrupt service routines (ISRs) associated with all the devices that share
the IRQ.
4. Terminate by jumping to the ret_from_intr( ) address.
