The Inter-Core Interrupt unit (ICI) handles the inter-core interrupts and acknowledgments between any two cores to handle asynchronous communication events.

See chapter "26.3 Inter-Core Interrupt Unit" of ARC HS databook.

Note this feature is only applicable to real SMP (Symmetric Multi-Processor) system, so it requires initial bring-up of SMP for ARC in QEMU (if there's anything to be done at all).