docs: add notes on handler dispatch order

docs/en/api-reference/system/esp_event.rst

@@ -186,6 +186,17 @@ If the hypothetical event ``MY_EVENT_BASE``, ``MY_OTHER_EVENT_ID`` is posted, on
 
 If the hypothetical event ``MY_OTHER_EVENT_BASE``, ``MY_OTHER_EVENT_ID`` is posted, only ``run_on_event_3`` would execute.
 
+Handler Registration and Handler Dispatch Order
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The general rule is that for handlers that match a certain posted event during dispatch, those which are registered first also gets executed first. The user can then control which handlers get executed first by
+registering them before other handlers, provided that all registrations are performed using a single task.
+If the user plans to take advantage of this behavior, caution must be exercised if there are multiple tasks registering handlers. While the 'first registered, first executed'
+behavior still holds true, the task which gets executed first will also get their handlers registered first. Handlers registered one after the other by a single task
+will still be dispatched in the order relative to each other, but if that task gets pre-empted in between registration by another task which also registers handlers; then during dispatch those
+handlers will also get executed in between.
+
+
 Event loop profiling
 --------------------