This commit introduces all the necessary changes for
enabling the usage of shared interrupts.
This works by using a second interrupt table: _shared_sw_isr_table
which keeps track of all of the ISR/arg pairs sharing the same
interrupt line. Whenever a second ISR/arg pair is registered
on the same interrupt line using IRQ_CONNECT(), the entry in
_sw_isr_table will be overwriten by a
(shared_isr, _shared_sw_isr_table[irq]) pair. In turn, shared_isr()
will invoke all of the ISR/arg pairs registered on the same
interrupt line.
This feature only works statically, meaning you can only make use
of shared interrupts using IRQ_CONNECT(). Attempting to dynamically
register a ISR/arg pair will overwrite the hijacked _sw_isr_table
entry.
Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
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