Support the remote devices on the remote processor via the RPMSG bus on
i.MX platform.

The expected DTS layout structure is following:

    cm33: remoteproc-cm33 {
             compatible = "fsl,imx8ulp-cm33";

             rpmsg {
                     rpmsg-io-channel {
                             gpio@0 {
                                     compatible = "fsl,imx-rpmsg-gpio";
                                     reg = <0>;
                             };

                             gpio@1 {
                                     compatible = "fsl,imx-rpmsg-gpio";
                                     reg = <1>;
                             };

                             ...
                     };

                     rpmsg-i2c-channel {
                             i2c@0 {
                                     compatible = "fsl,imx-rpmsg-i2c";
                                     reg = <0>;
                             };
                     };

                     ...
             };
     };

Changes in v2:
 - re-implemented the gpio driver per Linus Walleij's feedback by using
   GPIOLIB_IRQCHIP helper library.
 - fix various format issue per Mathieu/Peng 's review comments.
 - update the yaml doc per Rob's feedback

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>
Cc: Linus Walleij <linus.walleij@linaro.org>

Shenwei Wang (4):
  dt-bindings: remoteproc: imx_rproc: Add "rpmsg" subnode support
  remoteproc: imx_rproc: Populate devices under "rpmsg" subnode
  gpio: imx-rpmsg: add imx-rpmsg GPIO driver
  arm64: dts: imx8ulp: Add rpmsg node under imx_rproc

 .../bindings/remoteproc/fsl,imx-rproc.yaml    | 129 +++++
 arch/arm64/boot/dts/freescale/imx8ulp.dtsi    |  27 +
 drivers/gpio/Kconfig                          |  17 +
 drivers/gpio/Makefile                         |   1 +
 drivers/gpio/gpio-imx-rpmsg.c                 | 488 ++++++++++++++++++
 drivers/remoteproc/imx_rproc.c                | 126 +++++
 include/linux/rpmsg/imx_rpmsg.h               |  48 ++
 7 files changed, 836 insertions(+)
 create mode 100644 drivers/gpio/gpio-imx-rpmsg.c
 create mode 100644 include/linux/rpmsg/imx_rpmsg.h

--
2.43.0