diff --git a/Documentation/devicetree/bindings/arm/xen.txt b/Documentation/devicetree/bindings/arm/xen.txt
index db5c56db30ec..61d77acbeb5e 100644
--- a/Documentation/devicetree/bindings/arm/xen.txt
+++ b/Documentation/devicetree/bindings/arm/xen.txt
@@ -7,15 +7,17 @@ the following properties:
 	compatible = "xen,xen-<version>", "xen,xen";
   where <version> is the version of the Xen ABI of the platform.
 
-- reg: specifies the base physical address and size of a region in
-  memory where the grant table should be mapped to, using an
-  HYPERVISOR_memory_op hypercall. The memory region is large enough to map
-  the whole grant table (it is larger or equal to gnttab_max_grant_frames()).
-  This property is unnecessary when booting Dom0 using ACPI.
+- reg: specifies the base physical address and size of the regions in memory
+  where the special resources should be mapped to, using an HYPERVISOR_memory_op
+  hypercall.
+  Region 0 is reserved for mapping grant table, it must be always present.
+  The memory region is large enough to map the whole grant table (it is larger
+  or equal to gnttab_max_grant_frames()).
+  Regions 1...N are extended regions (unused address space) for mapping foreign
+  GFNs and grants, they might be absent if there is nothing to expose.
 
 - interrupts: the interrupt used by Xen to inject event notifications.
   A GIC node is also required.
-  This property is unnecessary when booting Dom0 using ACPI.
 
 To support UEFI on Xen ARM virtual platforms, Xen populates the FDT "uefi" node
 under /hypervisor with following parameters: