arm64: dts: apple: Add common SMC hwmon infrastructure

Apple's System Management Controller exposes the readings
from numerous sensors scattered around the SoC and elsewhere
in the machine. Some of these sensors are reliably common
on all devices, whereas others are exposed at SMC keys
specific to either the SoC or even the particular device.

To account for this and expose the right sensors for the
right device without tedious Devicetree duplication, we
can include fragments of increasing specificity in the
per-device .dts files such that the individual keys
(of which there are potentially hundreds) do not need to
be copied in for every device.

Add the initial set of SMC hwmon sensors that are common
to multiple devices so that they can be included in
the per-device Devicetrees.

Co-developed-by: Janne Grunau <j@jannau.net>
Signed-off-by: Janne Grunau <j@jannau.net>
Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
Link: https://patch.msgid.link/20260714-smc-subdev-dt-v2-5-13fa78873121@gmail.com
Signed-off-by: Sven Peter <sven@kernel.org>

arch/arm64/boot/dts/apple/hwmon-common.dtsi

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0+ OR MIT
+/*
+ * hwmon sensors expected on all systems
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+&smc_hwmon {
+	power-PSTR {
+		apple,key-id = "PSTR";
+		label = "Total System Power";
+	};
+
+	power-PDTR {
+		apple,key-id = "PDTR";
+		label = "AC Input Power";
+	};
+
+	power-PMVR {
+		apple,key-id = "PMVR";
+		label = "3.8 V Rail Power";
+	};
+
+	temperature-TH0x {
+		apple,key-id = "TH0x";
+		label = "NAND Flash Temperature";
+	};
+
+	voltage-VD0R {
+		apple,key-id = "VD0R";
+		label = "AC Input Voltage";
+	};
+
+	current-ID0R {
+		apple,key-id = "ID0R";
+		label = "AC Input Current";
+	};
+};

arch/arm64/boot/dts/apple/hwmon-fan-dual.dtsi

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0+ OR MIT
+/*
+ * Copyright The Asahi Linux Contributors
+ *
+ * Fan hwmon sensors for machines with 2 fan.
+ */
+
+#include "hwmon-fan.dtsi"
+
+&smc_hwmon {
+	fan-F0Ac {
+		label = "Fan 1";
+	};
+
+	fan-F1Ac {
+		apple,key-id = "F1Ac";
+		label = "Fan 2";
+		apple,fan-minimum = "F1Mn";
+		apple,fan-maximum = "F1Mx";
+		apple,fan-target = "F1Tg";
+		apple,fan-mode = "F1Md";
+	};
+};

arch/arm64/boot/dts/apple/hwmon-fan.dtsi

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0+ OR MIT
+/*
+ * Copyright The Asahi Linux Contributors
+ *
+ * Fan hwmon sensors for machines with a single fan.
+ */
+
+&smc_hwmon {
+	fan-F0Ac {
+		apple,key-id = "F0Ac";
+		label = "Fan";
+		apple,fan-minimum = "F0Mn";
+		apple,fan-maximum = "F0Mx";
+		apple,fan-target = "F0Tg";
+		apple,fan-mode = "F0Md";
+	};
+};

arch/arm64/boot/dts/apple/hwmon-laptop.dtsi

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0+ OR MIT
+/*
+ * hwmon sensors expected on all laptops
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+&smc_hwmon {
+	power-PHPC {
+		apple,key-id = "PHPC";
+		label = "Heatpipe Power";
+	};
+
+	temperature-TB0T {
+		apple,key-id = "TB0T";
+		label = "Battery Hotspot";
+	};
+
+	temperature-TCHP {
+		apple,key-id = "TCHP";
+		label = "Charge Regulator Temp";
+	};
+
+	temperature-TW0P {
+		apple,key-id = "TW0P";
+		label = "WiFi/BT Module Temp";
+	};
+
+	voltage-SBAV {
+		apple,key-id = "SBAV";
+		label = "Battery Voltage";
+	};
+
+	voltage-VD0R {
+		apple,key-id = "VD0R";
+		label = "Charger Input Voltage";
+	};
+};

arch/arm64/boot/dts/apple/hwmon-mini.dtsi

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0+ OR MIT
+/*
+ * hwmon sensors common to the Mac mini desktop
+ * models, but not the Studio or Pro.
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include "hwmon-fan.dtsi"
+
+&smc_hwmon {
+	temperature-TW0P {
+		apple,key-id = "TW0P";
+		label = "WiFi/BT Module Temp";
+	};
+};