[API] Sub devices and areas (#8544)

Co-authored-by: J. Nick Koston <nick@koston.org>
Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>
Co-authored-by: J. Nick Koston <nick+github@koston.org>

esphome/config_validation.py

@@ -1,5 +1,7 @@
 """Helpers for config validation using voluptuous."""
 
+from __future__ import annotations
+
 from contextlib import contextmanager
 from dataclasses import dataclass
 from datetime import datetime
@@ -29,6 +31,7 @@ from esphome.const import (
     CONF_COMMAND_RETAIN,
     CONF_COMMAND_TOPIC,
     CONF_DAY,
+    CONF_DEVICE_ID,
     CONF_DISABLED_BY_DEFAULT,
     CONF_DISCOVERY,
     CONF_ENTITY_CATEGORY,
@@ -355,6 +358,13 @@ def icon(value):
     )
 
 
+def sub_device_id(value: str | None) -> core.ID:
+    # Lazy import to avoid circular imports
+    from esphome.core.config import Device
+
+    return use_id(Device)(value)
+
+
 def boolean(value):
     """Validate the given config option to be a boolean.
 
@@ -1896,6 +1906,7 @@ ENTITY_BASE_SCHEMA = Schema(
         Optional(CONF_DISABLED_BY_DEFAULT, default=False): boolean,
         Optional(CONF_ICON): icon,
         Optional(CONF_ENTITY_CATEGORY): entity_category,
+        Optional(CONF_DEVICE_ID): sub_device_id,
     }
 )
 
@@ -1964,7 +1975,7 @@ class Version:
         return f"{self.major}.{self.minor}.{self.patch}"
 
     @classmethod
-    def parse(cls, value: str) -> "Version":
+    def parse(cls, value: str) -> Version:
         match = re.match(r"^(\d+).(\d+).(\d+)-?\w*$", value)
         if match is None:
             raise ValueError(f"Not a valid version number {value}")