The mct on exynos uses an interrupt map so we add support now. Devices
represent their interrupts either through a combination of interrupt-parent
and interrupts properties, where the 'interrupts' property is an array of
one or more interrupt specifiers; or through a combination of an
interrupt-parent that points to an interrupt-map, where the interrupt-map
contains 2 or more entries consisting of an index, a pointer to an
interrupt-controller, and a specifier for that controller.
This code adds the ability to walk the interrupt-map and return a specifier.
Unfortunately, the addition requires changing the interface to the
interrupt-controllers' _establish and _intstr functions, so this check in
contains a rototill of the three existing fdt interrupt controllers to use
the new interface.
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