Why does Nios II ISR have context parameter?

[Altera_Forum]

Since an ISR already has access to global variables and registers, why do we need to have a "void* context" parameter in an ISR? 

 Since the term context is also used in then sense of device/application context and context switch where value of specific device registers is stored, why then is the same term used to pass optional information to an ISR in Nios II HAL?

[Altera_Forum]

While I have figured out other things about questions I posted earlier, this question really needs answer from someone that has access to esoteric knowledge. Since an interrupt already has access to global variables and thus regiters in memory map, it is not clear why someone would invent the concept of "context" passed to an ISR.