Docs: clarify serialization resolution order (#59750)

Author: jaymasiwal

airflow-core/docs/authoring-and-scheduling/serializers.rst

@@ -26,12 +26,23 @@ and efficiency.
 Serialization is a surprisingly hard job. Python out of the box only has support for serialization of primitives,
 like ``str`` and ``int`` and it loops over iterables. When things become more complex, custom serialization is required.
 
-Airflow out of the box supports three ways of custom serialization. Primitives are returned as is, without
-additional encoding, e.g. a ``str`` remains a ``str``. When it is not a primitive (or iterable thereof) Airflow
-looks for a registered serializer and deserializer in the namespace of ``airflow.sdk.serde.serializers``.
-If not found it will look in the class for a ``serialize()`` method or in case of deserialization a
-``deserialize(data, version: int)`` method. Finally, if the class is either decorated with ``@dataclass``
-or ``@attr.define`` it will use the public methods for those decorators.
+Serialization resolution order
+------------------------------
+
+Airflow resolves custom serialization in the following order:
+
+1. Primitive values (such as ``str`` or ``int``) and iterables of primitives
+   are returned as-is, without additional encoding.
+
+2. If the object is not a primitive, Airflow looks for a registered serializer
+   and deserializer in the ``airflow.sdk.serde.serializers`` namespace.
+
+3. If no registered serializer is found, Airflow checks whether the object
+   defines a ``serialize()`` method (and, for deserialization, a corresponding
+   ``deserialize(data, version: int)`` method).
+
+4. Finally, if the object is decorated with ``@dataclass`` or ``@attr.define``,
+   Airflow serializes the object using the public fields provided by those decorators.
 
 If you are looking to extend Airflow with a new serializer, it is good to know when to choose what way of serialization.
 Objects that are under the control of Airflow, i.e. residing under the namespace of ``airflow.*`` like