gen_defines: output the interrupt level of a node

Currently it is tedious to know the level of an interrupt for
a node in C. One would have to go through a very complex and
error prone macros to check if there's a parent interrupt
controller & if the controller has an interrupt number and thus
not a pseudo interrupt controller like the one found in
`rv32m1`. The level of a node is required to encode the
Zephyr's multi-level interrupt number

Since it is easier to do it in the `gen_defines` script, let's
do the heavy lifting there so that we can introduce new DT
macros to get the interrupt level very easily later.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>

doc/build/dts/macros.bnf

@@ -37,6 +37,7 @@ node-macro =/ %s"DT_N" path-id %s"_REG_NAME_" dt-name
               %s"_VAL_" ( %s"ADDRESS" / %s"SIZE")
 ; The interrupts property is also special.
 node-macro =/ %s"DT_N" path-id %s"_IRQ_NUM"
+node-macro =/ %s"DT_N" path-id %s"_IRQ_LEVEL"
 node-macro =/ %s"DT_N" path-id %s"_IRQ_IDX_" DIGIT "_EXISTS"
 node-macro =/ %s"DT_N" path-id %s"_IRQ_IDX_" DIGIT
               %s"_VAL_" dt-name [ %s"_EXISTS" ]

scripts/dts/gen_defines.py

@@ -484,6 +484,16 @@ def write_interrupts(node):
             name_controller_macro = f"{path_id}_IRQ_NAME_{str2ident(irq.name)}_CONTROLLER"
             name_vals.append((name_controller_macro, f"DT_{idx_controller_macro}"))
 
+    # Interrupt controller info
+    irqs = []
+    while node.interrupts is not None and len(node.interrupts) > 0:
+        irq = node.interrupts[0]
+        irqs.append(irq)
+        if node == irq.controller:
+            break
+        node = irq.controller
+    idx_vals.append((f"{path_id}_IRQ_LEVEL", len(irqs)))
+
     for macro, val in idx_vals:
         out_dt_define(macro, val)
     for macro, val in name_vals: