diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a100.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a100.dtsi
index 7cb06b19b5a5..d8391663fd1d 100644
--- a/arch/arm64/boot/dts/allwinner/sun50i-a100.dtsi
+++ b/arch/arm64/boot/dts/allwinner/sun50i-a100.dtsi
@@ -87,6 +87,22 @@ osc32k: osc32k-clk {
 		#clock-cells = <0>;
 	};
 
+	reserved-memory {
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
+		/*
+		 * 256 KiB reserved for Trusted Firmware-A (BL31).
+		 * This is added by BL31 itself, but some bootloaders fail
+		 * to propagate this into the DTB handed to kernels.
+		 */
+		secmon@40000000 {
+			reg = <0x0 0x40000000 0x0 0x40000>;
+			no-map;
+		};
+	};
+
 	timer {
 		compatible = "arm,armv8-timer";
 		interrupts = <GIC_PPI 13