You can access a simple memory-mapped device from Linux userspace through the use of /dev/mem. The Epiphany SDK used this interface before Adapteva did a Linux driver. However, I am not sure if you can actually use interrupts without at least a simple driver. Using /dev/mem is considered bad style, since your application then requires root access and is able to crash your Linux system easily, but it might suffice.
I don't know if Linux provides generic device drivers for simple devices. If that is the case (I think it is), then you just need to describe your IP (memory addresses, interrupt vector etc) in the device-tree and use that driver. But I don't have experience in those areas.