Some ports (e.g. Synopsys DesignWare 8250) have special requirements for handling the interrupts. Allow these platforms to specify their own interrupt handler that will override the default. serial8250_handle_irq() is provided so that platforms can extend the IRQ handler rather than completely replacing it. Signed-off-by: Jamie Iles <jamie@jamieiles.com> Acked-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>