diff --git a/homeassistant/components/knx/storage/knx_selector.py b/homeassistant/components/knx/storage/knx_selector.py
index 8bba12633c8..5adf242c16b 100644
--- a/homeassistant/components/knx/storage/knx_selector.py
+++ b/homeassistant/components/knx/storage/knx_selector.py
@@ -8,6 +8,7 @@ import voluptuous as vol
 
 from ..validation import ga_validator, maybe_ga_validator, sync_state_validator
 from .const import CONF_DPT, CONF_GA_PASSIVE, CONF_GA_STATE, CONF_GA_WRITE
+from .util import dpt_string_to_dict
 
 
 class AllSerializeFirst(vol.All):
@@ -179,14 +180,6 @@ class GASelector(KNXSelectorBase):
     def serialize(self) -> dict[str, Any]:
         """Serialize the selector to a dictionary."""
 
-        def dpt_to_dict(dpt: str) -> dict[str, int | None]:
-            """Convert a DPT string to a dictionary."""
-            dpt_num = dpt.split(".")
-            return {
-                "main": int(dpt_num[0]),
-                "sub": int(dpt_num[1]) if len(dpt_num) > 1 else None,
-            }
-
         options: dict[str, Any] = {
             "write": {"required": self.write_required} if self.write else False,
             "state": {"required": self.state_required} if self.state else False,
@@ -197,12 +190,12 @@ class GASelector(KNXSelectorBase):
                 {
                     "value": item.value,
                     "translation_key": item.value.replace(".", "_"),
-                    "dpt": dpt_to_dict(item.value),  # used to filter DPTs in dropdown
+                    "dpt": dpt_string_to_dict(item.value),  # used for filtering GAs
                 }
                 for item in self.dpt
             ]
         if self.valid_dpt is not None:
-            options["validDPTs"] = [dpt_to_dict(dpt) for dpt in self.valid_dpt]
+            options["validDPTs"] = [dpt_string_to_dict(dpt) for dpt in self.valid_dpt]
 
         return {
             "type": self.selector_type,
diff --git a/homeassistant/components/knx/storage/serialize.py b/homeassistant/components/knx/storage/serialize.py
index 37ee53df40b..1b453a24562 100644
--- a/homeassistant/components/knx/storage/serialize.py
+++ b/homeassistant/components/knx/storage/serialize.py
@@ -35,7 +35,9 @@ def knx_serializer(
     return UNSUPPORTED  # type: ignore[no-any-return]
 
 
-def get_serialized_schema(platform: Platform) -> dict | list | None:
+def get_serialized_schema(
+    platform: Platform,
+) -> dict[str, Any] | list[dict[str, Any]] | None:
     """Get the schema for a specific platform."""
     if knx_schema := KNX_SCHEMA_FOR_PLATFORM.get(platform):
         return convert(knx_schema, custom_serializer=knx_serializer)  # type: ignore[no-any-return]
diff --git a/homeassistant/components/knx/storage/util.py b/homeassistant/components/knx/storage/util.py
index a3831070a7e..978a0568455 100644
--- a/homeassistant/components/knx/storage/util.py
+++ b/homeassistant/components/knx/storage/util.py
@@ -3,11 +3,29 @@
 from functools import partial
 from typing import Any
 
+from xknx.typing import DPTMainSubDict
+
 from homeassistant.helpers.typing import ConfigType
 
 from .const import CONF_DPT, CONF_GA_PASSIVE, CONF_GA_STATE, CONF_GA_WRITE
 
 
+def dpt_string_to_dict(dpt: str) -> DPTMainSubDict:
+    """Convert a DPT string to a typed dictionary with main and sub components.
+
+    Examples:
+        >>> dpt_string_to_dict("1.010")
+        {'main': 1, 'sub': 10}
+        >>> dpt_string_to_dict("5")
+        {'main': 5, 'sub': None}
+    """
+    dpt_num = dpt.split(".")
+    return DPTMainSubDict(
+        main=int(dpt_num[0]),
+        sub=int(dpt_num[1]) if len(dpt_num) > 1 else None,
+    )
+
+
 def nested_get(dic: ConfigType, *keys: str, default: Any | None = None) -> Any:
     """Get the value from a nested dictionary."""
     for key in keys: