Context of sigio handler

[Yo_Frankie]

Hi,

in linux you can register a handler function, that is asynchronously called by a driver, when an event occurs.
The X Server documentation says for example:
"When a device emits events, a SIGIO is fired and the xf86SIGIO() handler is called"

The device driver usually runs in the interrupt context or in the context of another process (but not in the context of that process, that registered the handler).
How is the handler function called? Is the context immediately switched to the process having registered the handler function and the handler function address is loaded to the program counter register?

I see, there's something like a signal handling context? Still the virtual address space has to be switched to the signal handling process, to be able to call the handler function, hasn't it? Therefore things like the translation look aside buffer have to be invalidated?