data merge DOC extend description about using lyd_merge_to_ctx()
diff --git a/src/tree_data.h b/src/tree_data.h
index 9b1df71..46eef2b 100644
--- a/src/tree_data.h
+++ b/src/tree_data.h
@@ -849,7 +849,8 @@
*
* @param[in] trg Top-level (or an RPC output child) data tree to merge to. Must be valid. If its context
* differs from the specified \p ctx of the result, the provided data tree is freed and the new
- * tree in the required context is returned on success.
+ * tree in the required context is returned on success. To keep the \p trg tree, convert it to the
+ * target context using lyd_dup_to_ctx() and then call lyd_merge() instead of lyd_merge_to_ctx().
* @param[in] src Data tree to merge \p target with. Must be valid (at least as a subtree).
* @param[in] options Bitmask of the following option flags:
* - #LYD_OPT_DESTRUCT - spend \p source in the function, otherwise \p source is left untouched,