docs(pm):add uart wakeup description when pd top

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

@@ -191,6 +191,11 @@ When {IDF_TARGET_NAME} receives UART input from external devices, it is often ne
 
 :cpp:func:`esp_sleep_enable_uart_wakeup` function can be used to enable this wakeup source.
 
+    .. only:: esp32c6 or esp32h2
+
+       .. note::
+
+           In Light-sleep mode, setting Kconfig option :ref:`CONFIG_PM_POWER_DOWN_PERIPHERAL_IN_LIGHT_SLEEP` will invalidate UART wakeup.
 
 Power-down of RTC Peripherals and Memories
 ------------------------------------------

docs/zh_CN/api-reference/system/sleep_modes.rst

@@ -191,6 +191,11 @@ UART 唤醒（仅适用于 Light-sleep 模式）
 
 可调用 :cpp:func:`esp_sleep_enable_uart_wakeup` 函数来启用此唤醒源。
 
+    .. only:: esp32c6 or esp32h2
+
+       .. note::
+
+           在 Light-sleep 模式下，设置 Kconfig 选项 :ref:`CONFIG_PM_POWER_DOWN_PERIPHERAL_IN_LIGHT_SLEEP` 将使 UART 唤醒失效。
 
 RTC 外设和内存断电
 ---------------------