diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6571fbf..78cdf6a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3675,7 +3675,11 @@
 			[KNL, SMP] Set scheduler's default relax_domain_level.
 			See Documentation/cgroup-v1/cpusets.txt.
 
-	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
+	reserve=	[KNL,BUGS] Force kernel to ignore I/O ports or memory
+			Format: <base1>,<size1>[,<base2>,<size2>,...]
+			Reserve I/O ports or memory so the kernel won't use
+			them.  If <base> is less than 0x10000, the region
+			is assumed to be I/O ports; otherwise it is memory.
 
 	reservetop=	[X86-32]
 			Format: nn[KMG]