Add mailbox device tree node. This work is based on the vendor kernel [1].

Link: https://github.com/revyos/thead-kernel.git [1]

Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
---
 arch/riscv/boot/dts/thead/th1520.dtsi | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
index 6992060e6a54..89de5634d3d3 100644
--- a/arch/riscv/boot/dts/thead/th1520.dtsi
+++ b/arch/riscv/boot/dts/thead/th1520.dtsi
@@ -520,6 +520,22 @@ timer7: timer@ffffc3303c {
 			status = "disabled";
 		};
 
+		mbox_910t: mailbox@ffffc38000 {
+			compatible = "thead,th1520-mbox";
+			reg = <0xff 0xffc38000 0x0 0x6000>,
+			      <0xff 0xffc40000 0x0 0x6000>,
+			      <0xff 0xffc4c000 0x0 0x2000>,
+			      <0xff 0xffc54000 0x0 0x2000>;
+			reg-names = "local", "remote-icu0", "remote-icu1", "remote-icu2";
+			clocks = <&clk CLK_MBOX0>, <&clk CLK_MBOX1>, <&clk CLK_MBOX2>,
+				 <&clk CLK_MBOX3>;
+			clock-names = "clk-local", "clk-remote-icu0", "clk-remote-icu1",
+				      "clk-remote-icu2";
+			interrupt-parent = <&plic>;
+			interrupts = <28 IRQ_TYPE_LEVEL_HIGH>;
+			#mbox-cells = <1>;
+		};
+
 		ao_gpio0: gpio@fffff41000 {
 			compatible = "snps,dw-apb-gpio";
 			reg = <0xff 0xfff41000 0x0 0x1000>;
-- 
2.34.1