[PATCH v2] docs: add some clarification to xenstore-migration.md

[Juergen Gross <jgross@xxxxxxxx>]

The Xenstore migration document is missing the specification that a
node record must be preceded by the record of its parent node in case
of live update.

Add that missing part.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- rephrase to cover non-LU case, too (Julien Grall)
---
 docs/designs/xenstore-migration.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/docs/designs/xenstore-migration.md 
b/docs/designs/xenstore-migration.md
index 5f1155273e..b94af7fd7c 100644
--- a/docs/designs/xenstore-migration.md
+++ b/docs/designs/xenstore-migration.md
@@ -316,6 +316,11 @@ a _committed_ node (globally visible in xenstored) or a 
_pending_ node (created
 or modified by a transaction for which there is also a `TRANSACTION_DATA`
 record previously present).
 
+Each _committed_ node in the stream is required to have an already known parent
+node. A parent node is known if it was either in the node data base before the
+stream was started to be processed, or if a `NODE_DATA` record for that parent
+node has already been processed in the stream.
+
 
 ```
     0       1       2       3    octet
-- 
2.34.1