dt-bindings/irqchip/mbigen: add example of MBIGEN generate SPIs

hulk inclusion
category: feature
bugzilla: 46791
CVE: N/A

-------------------------------------------------

Now MBIGEN can support to generate SPIs by writing
GICD_SETSPIR. Add dt example to help document.
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: Nzhangyi (F) <yi.zhang@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>

Documentation/devicetree/bindings/interrupt-controller/hisilicon,mbigen-v2.txt

@@ -10,7 +10,7 @@ Hisilicon designed mbigen to collect and generate interrupt.
 
 
 Non-pci devices can connect to mbigen and generate the
-interrupt by writing ITS register.
+interrupt by writing GICD or ITS register.
 
 The mbigen chip and devices connect to mbigen have the following properties:
 
@@ -64,6 +64,13 @@ Examples:
 				num-pins = <2>;
 				#interrupt-cells = <2>;
 			};
+
+			mbigen_spi_example:spi_example {
+				interrupt-controller;
+				msi-parent = <&gic>;
+				num-pins = <2>;
+				#interrupt-cells = <2>;
+			};
 	};
 
 Devices connect to mbigen required properties:
@@ -82,3 +89,11 @@ Examples:
 		interrupts =	<656 1>,
 				<657 1>;
 	};
+
+	spi_example: spi0@0 {
+		compatible = "spi,example";
+		reg = <0 0 0 0>;
+		interrupt-parent = <&mbigen_spi_example>;
+		interrupts = <13 4>,
+			     <14 4>;
+	};