of/irq: Handle explicit interrupt parent

If an interrupt controller is used as a proxy, it may have an
"interrupt-parent" property, but lack "interrupts" and
"interrupts-extended" properties. In that case, the "interrupt-parent"
property in the interrupt controller node is ignored, causing the
interrupt controller to fail to probe, and leading to system boot
failures or crashes.

Fix this by also considering an explicit "interrupt-parent" property in
the interrupt controller node itself.

Fixes: 1b1f04d8271e7ba7 ("of/irq: Ignore interrupt parent for nodes without interrupts")
Reported-by: Marek Szyprowski <[e-mail]>
Closes: https://lore.kernel.org/[e-mail]
Reported-by: Mark Brown <[e-mail]>
Closes: https://lore.kernel.org/[e-mail]
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Tested-by: Marek Szyprowski <[e-mail]>
Tested-by: Mark Brown <[e-mail]>
Link: https://patch.msgid.link/e8966[e-mail]
Signed-off-by: Rob Herring (Arm) <[e-mail]>

drivers/of/irq.c

···
 		desc->interrupt_parent = of_parse_phandle(np, "interrupts-extended", 0);
 		if (!desc->interrupt_parent && of_property_present(np, "interrupts"))
 			desc->interrupt_parent = of_irq_find_parent(np);
+		else if (!desc->interrupt_parent)
+			desc->interrupt_parent = of_parse_phandle(np, "interrupt-parent", 0);
 		if (desc->interrupt_parent == np) {
 			of_node_put(desc->interrupt_parent);
 			desc->interrupt_parent = NULL;