libyang DOC add brief thread information
diff --git a/src/libyang.h b/src/libyang.h
index 7733def..ddf9bc3 100644
--- a/src/libyang.h
+++ b/src/libyang.h
@@ -132,6 +132,22 @@
*/
/**
+ * @page howtoThreads Threading Limitations
+ *
+ * @section context Context
+ *
+ * It is safe to read from ::ly_ctx structure concurrently and use its dictionary, which is protected by a lock.
+ * Thread-safe functions include any ones working with data trees (only context dictionary is accessed) and all
+ * the `ly_ctx_get_*()` functions. Generally, they are the functions with `const` context parameter.
+ *
+ * @section data Data Trees
+ *
+ * Data trees are not internally synchronized so the general safe practice of a single writer **or** several concurrent
+ * readers should be followed. Specifically, only the functions with non-const ::lyd_node parameters modify the node(s)
+ * and no concurrent execution of such functions should be allowed on a single data tree or subtrees of one.
+ */
+
+/**
* @internal
* @page internals Developers' Notes
* @tableofcontents