[PATCH 0/2] WK2xxx SPI to UART bridge driver

[zjzhao]

This series adds a driver for the WK2xxx SPI to UART bridge ICs
(WK2124, WK2132, WK2168, WK2202 and WK2204) from WKmic (Chengdu Weikai
Microelectronics). Each IC exposes two or four full-duplex UART channels
with 256-byte RX/TX FIFOs through a single SPI slave interface and one
interrupt line.

The driver is a rework of the vendor driver (https://github.com/britus/
wk2xxx) modeled after the NXP sc16is7xx driver. It registers ttyWK0..N
lines (IDA-allocated), uses devm_request_threaded_irq with a kthread
worker for register access, falls back to polling when the interrupt
line is not described, and supports hardware flow control and RS485
where the IC provides them.

Patch 1 adds the driver, the PORT_WK2XXX (124) type and the
SERIAL_WK2XXX Kconfig option. Patch 2 documents the DT binding and
registers the wkmic vendor prefix.

Tested on Raspberry Pi 5 boards (EDATEC IPC1200 with WK2132 on SPI0 and
SBC2300 with WK2204 on SPI1); loopback TX/RX tests pass.

zjzhao (2):
  serial: wk2xxx: Add WK2xxx SPI UART driver
  dt-bindings: serial: Document WK2xxx SPI UART bindings

 .../bindings/serial/wkmic,wk2xxx.yaml         |   69 +
 .../devicetree/bindings/vendor-prefixes.yaml  |    2 +
 drivers/tty/serial/Kconfig                    |   17 +
 drivers/tty/serial/Makefile                   |    1 +
 drivers/tty/serial/wk2xxx.c                   | 1245 +++++++++++++++++
 include/uapi/linux/serial_core.h              |    3 +
 6 files changed, 1337 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/wkmic,wk2xxx.yaml
 create mode 100644 drivers/tty/serial/wk2xxx.c


base-commit: bc35965f6940a9bf834d54187b6088b8eb09206d
-- 
2.43.0