Merge pull request #36407 from johnlinp/add-note-pre-provisioned-snapshot

Add a note on the pre-provisioned snapshot scenario

Author: k8s-ci-robot

content/en/docs/concepts/storage/volume-snapshots.md

@@ -155,6 +155,8 @@ of the `sourceVolumeMode` field can be either `Filesystem` or `Block`. If the
 source volume mode is not specified, Kubernetes treats the snapshot as if the 
 source volume's mode is unknown.
 
+`volumeSnapshotRef` is the reference of the corresponding `VolumeSnapshot`. Note that when the `VolumeSnapshotContent` is being created as a pre-provisioned snapshot, the `VolumeSnapshot` referenced in `volumeSnapshotRef` might not exist yet.
+
 ## Converting the volume mode of a Snapshot {#convert-volume-mode}
 
 If the `VolumeSnapshots` API installed on your cluster supports the `sourceVolumeMode`