ACPI: docs: enumeration: Update UART serial bus resource documentation

In some cases UART serial bus resource may be represented by struct
serdev_device.

Fixes: 53c7626 ("serdev: Add ACPI support")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: andy-shev

Documentation/firmware-guide/acpi/enumeration.rst

@@ -19,16 +19,17 @@ possible we decided to do following:
     platform devices.
 
   - Devices behind real busses where there is a connector resource
-    are represented as struct spi_device or struct i2c_device
-    (standard UARTs are not busses so there is no struct uart_device).
+    are represented as struct spi_device or struct i2c_device. Note
+    that standard UARTs are not busses so there is no struct uart_device,
+    although some of them may be represented by sturct serdev_device.
 
 As both ACPI and Device Tree represent a tree of devices (and their
 resources) this implementation follows the Device Tree way as much as
 possible.
 
-The ACPI implementation enumerates devices behind busses (platform, SPI and
-I2C), creates the physical devices and binds them to their ACPI handle in
-the ACPI namespace.
+The ACPI implementation enumerates devices behind busses (platform, SPI,
+I2C, and in some cases UART), creates the physical devices and binds them
+to their ACPI handle in the ACPI namespace.
 
 This means that when ACPI_HANDLE(dev) returns non-NULL the device was
 enumerated from ACPI namespace. This handle can be used to extract other