Comment 0 for bug 1945938

[Impact]

The xr-usb-serial custom (downstream vendor) driver was added in Xenial LTS kernel
to add support for USB UART chips:
Family: USB UART
Part Numbers:
    XR21V1410, XR21V1412, XR21V1414,
    XR21B1411, XR21B1420, XR21B1422,
    XR21B1424, XR22801, XR22802,
    XR22804

[Fix]
In 5.13.x, support for these devices was added to the kernel via. following patch series:
Link: https://<email address hidden>/

There have been long term maintenance challenges with the downstream vendor driver
over the period of time (since 4.4.y based Xenial LTS). Now that upstream driver
supports most of the above part numbers, let's remove this redundant out-of-tree driver.

[Test]
The driver was functionally verified to work fine with XR21V1412. The support for
other chips with part numbers mentioned above are also supported with the above
patch series.

[Where problems could occur]
Low. The downstream driver was designed to work with specific BIOS configs only
defined on an IoT GW project which is locked to use only Xenial ESM and Bionic LTS
kernels, there is a low chance of regression on the Impish series.