Document availability and meaning of unmapped DAMOS filter type on
design document.  Since introduction of the type requires no additional
user ABI, usage and ABI document need no update.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 6a66aa0833fd..5af991551a86 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -617,6 +617,8 @@ Below ``type`` of filters are currently supported.
           scheme.
     - hugepage_size
         - Applied to pages that managed in a given size range.
+    - unmapped
+        - Applied to pages that unmapped.
 
 To know how user-space can set the filters via :ref:`DAMON sysfs interface
 <sysfs_interface>`, refer to :ref:`filters <sysfs_filters>` part of the
-- 
2.39.5