usb: xhci-pci: add AMD Promontory 21 PCI glue

AMD Promontory 21 (PROM21) xHCI PCI functions use the common xhci-pci
core for USB operation, but also expose controller-specific sensor data.
Add a small PROM21 PCI glue driver for AMD 1022:43fc and 1022:43fd
controllers.

The glue delegates USB host operation to the common xhci-pci core and
publishes a "hwmon" auxiliary device with parent-provided MMIO data.
Auxiliary device creation failure is logged but does not fail the xHCI
probe.

Make the PROM21 glue a hidden Kconfig tristate driven by the user-visible
SENSORS_PROM21_XHCI option. If sensor support is disabled, generic
xhci-pci binds PROM21 controllers normally. If sensor support is enabled,
the glue follows USB_XHCI_PCI.

This keeps the auxiliary device available for a modular sensor driver while
avoiding a built-in xhci-pci core handing PROM21 controllers to a glue
driver that is only available as a module during initramfs.

Assisted-by: Codex:gpt-5.5
Signed-off-by: Jihong Min <hurryman2212@gmail.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Tested-by: Yaroslav Isakov <yaroslav.isakov@gmail.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://patch.msgid.link/20260519000732.2334711-2-hurryman2212@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions