diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
index ff30728595ef..c4dfe7355c2d 100644
--- a/Documentation/ABI/testing/sysfs-bus-platform
+++ b/Documentation/ABI/testing/sysfs-bus-platform
@@ -42,3 +42,15 @@ Date:		August 2021
 Contact:	Barry Song <song.bao.hua@hisilicon.com>
 Description:
 		This attribute will show "msi" if <N> is a valid msi irq
+
+What:		/sys/bus/platform/devices/.../modalias
+Description:
+		Same as MODALIAS in the uevent at device creation.
+
+		A platform device that it is exposed via devicetree uses:
+
+			- of:N`of node name`T`type`
+
+		Other platform devices use, instead:
+
+			- platform:`driver name`