FriendlyELEC offers an optional heatsink and fan addon [1] for the
NanoPC-T6 and T6 LTS, which plugs in to the fan connector on the board
driven by pwm1. Add the fan as an active cooling device for the SoC package.
The PWM duty cycle values are taken from the vendor's source [2].

Signed-off-by: Hugh Cole-Baker <redacted>

[1]: https://www.friendlyelec.com/index.php?route=product/product&product_id=305
[2]: https://github.com/friendlyarm/kernel-rockchip/blob/4944602540b62f5aad139fe602a76cf7c3176128/arch/arm64/boot/dts/rockchip/rk3588-nanopi6-rev01.dts#L75-L90
---
Changes from v2: https://lore.kernel.org/linux-rockchip/20251109192128.72527-1-sigmaris@gmail.com/ (local)
* Set trip points to 55 and 65°C (Dragan)

Changes from v1: https://lore.kernel.org/linux-rockchip/20251026194858.92461-1-sigmaris@gmail.com/ (local)
* add the fan to the base board dtsi instead of overlay (Heiko)
* just use 2 trip points for warm and hot temperatures (Dragan, Alexey)

 .../boot/dts/rockchip/rk3588-nanopc-t6.dtsi   | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/arch/arm64/boot/dts/rockchip/rk3588-nanopc-t6.dtsi b/arch/arm64/boot/dts/rockchip/rk3588-nanopc-t6.dtsi
index 90e7fe254491b..84b6b53f016ab 100644
--- a/arch/arm64/boot/dts/rockchip/rk3588-nanopc-t6.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3588-nanopc-t6.dtsi

@@ -11,6 +11,7 @@
 #include <dt-bindings/input/input.h>
 #include <dt-bindings/pinctrl/rockchip.h>
 #include <dt-bindings/soc/rockchip,vop2.h>
+#include <dt-bindings/thermal/thermal.h>
 #include <dt-bindings/usb/pd.h>
 #include "rk3588.dtsi"
 

@@ -89,6 +90,14 @@ usr_led: led-1 {
 		};
 	};
 
+	fan: pwm-fan {
+		compatible = "pwm-fan";
+		cooling-levels = <0 35 64 100 150 255>;
+		fan-supply = <&vcc5v0_sys>;
+		pwms = <&pwm1 0 50000 0>;
+		#cooling-cells = <2>;
+	};
+
 	sound {
 		compatible = "simple-audio-card";
 		pinctrl-names = "default";

@@ -590,6 +599,36 @@ &i2s6_8ch {
 	status = "okay";
 };
 
+&package_thermal {
+	polling-delay = <1000>;
+
+	trips {
+		package_warm: package-warm {
+			temperature = <55000>;
+			hysteresis = <2000>;
+			type = "active";
+		};
+
+		package_hot: package-hot {
+			temperature = <65000>;
+			hysteresis = <2000>;
+			type = "active";
+		};
+	};
+
+	cooling-maps {
+		map0 {
+			trip = <&package_warm>;
+			cooling-device = <&fan THERMAL_NO_LIMIT 1>;
+		};
+
+		map1 {
+			trip = <&package_hot>;
+			cooling-device = <&fan 2 THERMAL_NO_LIMIT>;
+		};
+	};
+};
+
 &pcie2x1l0 {
 	reset-gpios = <&gpio4 RK_PB3 GPIO_ACTIVE_HIGH>;
 	vpcie3v3-supply = <&vcc_3v3_pcie20>;