As the PVT sensors's "T" means thermal, add thermal zones for the
thermal sensors.

Because of the current lack of DVFS, only a critical trip point is added
now.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
---
 arch/riscv/boot/dts/thead/th1520.dtsi | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
index e9c81bdabed8a..a48eca5def606 100644
--- a/arch/riscv/boot/dts/thead/th1520.dtsi
+++ b/arch/riscv/boot/dts/thead/th1520.dtsi
@@ -701,4 +701,29 @@ gpio4: gpio-controller@0 {
 			};
 		};
 	};
+
+	thermal-zones {
+		cpu-thermal {
+			polling-delay-passive = <250>;
+			polling-delay = <15000>;
+
+			thermal-sensors = <&pvt 0>;
+
+			trips {
+				cpu_crit: crit-trip {
+					/* milliCelsius */
+					temperature = <110000>;
+					hysteresis = <2000>;
+					type = "critical";
+				};
+			};
+		};
+
+		ddrc-thermal {
+			polling-delay-passive = <250>;
+			polling-delay = <15000>;
+
+			thermal-sensors = <&pvt 1>;
+		};
+	};
 };
-- 
2.50.1