How to hook up a signal generated from VHDL to an internal NIOS II instance?

I'm working with some legacy VHDL code that I want to interface with a NIOS II core instead of an external processor. In specific, this signal is Active Low that was used as Interrupt for the external processor. I'm not seeing a clear description of how to go about doing this, despite many hours going thru the Interrupt Controller IP core docs. Any ideas? I'm assuming that it is something along the lines of supplying the signal name for the IRQ source somewhere, but I need just bit more details.

Thanks