Need clarity on legacy RC interrupt handling

[valmiki]

Hi,

Legacy interrupts are level triggered, but i see some RC drivers use 
flow handler "handle_simple_irq" instead why they are not using 
"handle_level_irq" ?

Why they are registering dummy_irq_chip with "handle_simple_irq", if 
they use this chip how the irq type is set for this virtual irq (level 
or edge).

Regards,
vamiki