doc UPDATE explicit data freeing function mention

Fixes #1732
Fixes #1733
diff --git a/src/context.h b/src/context.h
index a8aa29b..553892f 100644
--- a/src/context.h
+++ b/src/context.h
@@ -605,8 +605,8 @@
  * and free all structures internally used by libyang. If the caller uses
  * multiple contexts, the function should be called for each used context.
  *
- * All instance data are supposed to be freed before destroying the context.
- * Data models are destroyed automatically as part of ::ly_ctx_destroy() call.
+ * All instance data are supposed to be freed before destroying the context using ::lyd_free_all(), for example.
+ * Data models (schemas) are destroyed automatically as part of ::ly_ctx_destroy() call.
  *
  * Note that the data stored by user into the ::lysc_node.priv pointer are kept
  * untouched and the caller is responsible for freeing this private data.