Some recent(ish) Dell AIO devices have a backlight controller board
connected to an UART.

This UART has a DELL0501 HID with CID set to PNP0501 so that the UART is
still handled by 8250_pnp.c. Unfortunately there is no separate ACPI device
with an UartSerialBusV2() resource to model the backlight-controller.
This causes the kernel to create a /dev/ttyS0 char-device for the UART
instead of creating an in kernel serdev-controller + serdev-device pair
for a kernel backlight driver.

Use the existing acpi_quirk_skip_serdev_enumeration() mechanism to work
around this by returning skip=true for tty-ctrl parents with a HID
of DELL0501.

Like other cases where the UartSerialBusV2() resource is missing or broken
this will only create the serdev-controller device and the serdev-device
itself will need to be instantiated by platform code.

Unfortunately in this case there is no device for the platform-code
instantiating the serdev-device to bind to. So also create
a platform_device for this.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>