arm64: dts: apple: t8103,t60xx,t8112: Add SMC RTC node

The System Manager Controller of all M1/M2 SoCs supports the RTC
sub-device.

Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
Link: https://patch.msgid.link/20251215-macsmc-subdevs-v6-6-0518cb5f28ae@gmail.com
Signed-off-by: Sven Peter <sven@kernel.org>

Author: svenpeter42

arch/arm64/boot/dts/apple/t600x-die0.dtsi

@@ -44,6 +44,12 @@
 			nvmem-cell-names = "shutdown_flag", "boot_stage",
 				"boot_error_count", "panic_count";
 		};
+
+		rtc {
+			compatible = "apple,smc-rtc";
+			nvmem-cells = <&rtc_offset>;
+			nvmem-cell-names = "rtc_offset";
+		};
 	};
 
 	smc_mbox: mbox@290408000 {

arch/arm64/boot/dts/apple/t602x-die0.dtsi

@@ -121,6 +121,12 @@
 			nvmem-cell-names = "shutdown_flag", "boot_stage",
 				"boot_error_count", "panic_count";
 		};
+
+		rtc {
+			compatible = "apple,smc-rtc";
+			nvmem-cells = <&rtc_offset>;
+			nvmem-cell-names = "rtc_offset";
+		};
 	};
 
 	pinctrl_smc: pinctrl@2a2820000 {

arch/arm64/boot/dts/apple/t8103.dtsi

@@ -916,6 +916,12 @@
 				nvmem-cell-names = "shutdown_flag", "boot_stage",
 					"boot_error_count", "panic_count";
 			};
+
+			rtc {
+				compatible = "apple,smc-rtc";
+				nvmem-cells = <&rtc_offset>;
+				nvmem-cell-names = "rtc_offset";
+			};
 		};
 
 		smc_mbox: mbox@23e408000 {

arch/arm64/boot/dts/apple/t8112.dtsi

@@ -919,6 +919,12 @@
 				nvmem-cell-names = "shutdown_flag", "boot_stage",
 					"boot_error_count", "panic_count";
 			};
+
+			rtc {
+				compatible = "apple,smc-rtc";
+				nvmem-cells = <&rtc_offset>;
+				nvmem-cell-names = "rtc_offset";
+			};
 		};
 
 		smc_mbox: mbox@23e408000 {