riscv: dts: thead: Introduce power domain nodes with aon firmware

The DRM Imagination GPU requires a power-domain driver. In the T-HEAD
TH1520 SoC implements power management capabilities through the E902
core, which can be communicated with through the mailbox, using firmware
protocol.

Add AON node, which servers as a power-domain controller.

Signed-off-by: Michal Wilczynski <[email protected]>
Reviewed-by: Drew Fustini <[email protected]>
Signed-off-by: Drew Fustini <[email protected]>

Author: Michal Wilczynski

arch/riscv/boot/dts/thead/th1520.dtsi

@@ -6,6 +6,7 @@
 
 #include <dt-bindings/interrupt-controller/irq.h>
 #include <dt-bindings/clock/thead,th1520-clk-ap.h>
+#include <dt-bindings/power/thead,th1520-power.h>
 
 / {
 	compatible = "thead,th1520";
@@ -229,6 +230,13 @@
 		snps,blen = <0 0 64 32 0 0 0>;
 	};
 
+	aon: aon {
+		compatible = "thead,th1520-aon";
+		mboxes = <&mbox_910t 1>;
+		mbox-names = "aon";
+		#power-domain-cells = <1>;
+	};
+
 	soc {
 		compatible = "simple-bus";
 		interrupt-parent = <&plic>;