A schematic diagram for the interrupt logic. https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/109/903/894/236/634/197/original/e9b9ee21e9f039ea.png
From there, external interrupts go to some logic that prioritizes the interrupts, decides when the system can handle them (usually at the end of an instruction), and signals the microcode to execute the appropriate interrupt code.