arm64: dts: ti: k3-am62a-main: Add sa3_secproxy

Security Management Subsystem(SMS) has it's own unique secure
proxy as part of Security Accelerator (SA3) module. This is used
for communicating with ROM and for special usecases such as HSM
operations. This is in addition to the one in the main domain DMSS
subsystem that is used for general purpose communication.

Describe the node for use with bootloaders and firmware that require
this communication path which uses interrupts to corresponding micro
controller interrupt controller. Mark the node as disabled since this
instance does not have interrupts routed to the main processor by
default for a complete description of the node.

Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20230530165900.47502-3-nm@ti.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>

arch/arm64/boot/dts/ti/k3-am62a-main.dtsi

@@ -169,6 +169,21 @@
 		};
 	};
 
+	secure_proxy_sa3: mailbox@43600000 {
+		compatible = "ti,am654-secure-proxy";
+		#mbox-cells = <1>;
+		reg-names = "target_data", "rt", "scfg";
+		reg = <0x00 0x43600000 0x00 0x10000>,
+		      <0x00 0x44880000 0x00 0x20000>,
+		      <0x00 0x44860000 0x00 0x20000>;
+		/*
+		 * Marked Disabled:
+		 * Node is incomplete as it is meant for bootloaders and
+		 * firmware on non-MPU processors
+		 */
+		status = "disabled";
+	};
+
 	main_pmx0: pinctrl@f4000 {
 		compatible = "pinctrl-single";
 		reg = <0x00 0xf4000 0x00 0x2ac>;