On the MediaTek Genio 700 EVK, when installing Debian from an ISO image
on a USB disk plugged into the USB Type‑C port (which is the only USB
host port on this board), the installer fails to detect the USB disk
unless the typec and related mux drivers are present in the installer
initrd and loaded early.

This class of boards uses a USB Type‑C dual‑role port which cannot be
assumed to default to host mode without the Type‑C / mux policy drivers
being active. If the Type‑C state machine and mux drivers are not bound
during early boot, the USB pins may never be switched into the host
configuration. As a result, the
USB mass storage device is never properly probed by the kernel while
running the installer environment.

Concretely, on the Genio 700 EVK:

The only usable USB host connection for installation is via the Type‑C
port.
Without the typec core driver and the appropriate mux / retimer drivers
in the debian-installer initrd, the port stays in an disabled state.
The USB disk containing the ISO image is therefore not detected by the
installer, and the installation cannot proceed.

A merge request is available here:
https://salsa.debian.org/kernel-team/linux/-/merge_requests/1749/

And this has been reviewed from previous merge request since 4 month
ago and keeps rebase to the latest.
https://salsa.debian.org/kernel-team/linux/-/merge_requests/1577/

The previous merge request #1577 was includs mutiple modules.
So I've split the typec and mux part into a new merge request #1749
and closed #1577.

Please help to review if any thing still blocking the merge request
#1749.

Thanks!
Macpaul Lin