From: Vladimir Zapolskiy <redacted>

The change adds I2C device driver for TI DS90Ux9xx de-/serializers,
support of subdevice controllers is done in separate drivers, because
not all IC functionality may be needed in particular situations, and
this can be fine grained controlled in device tree.

The development of the driver was a collaborative work, the
contribution done by Balasubramani Vivekanandan includes:
* original implementation of the driver based on a reference driver,
* regmap powered interrupt controller support on serializers,
* support of implicitly or improperly specified in device tree ICs,
* support of device properties and attributes: backward compatible
  mode, low frequency operation mode, spread spectrum clock generator.

Contribution by Steve Longerbeam:
* added ds90ux9xx_read_indirect() function,
* moved number of links property and added ds90ux9xx_num_fpd_links(),
* moved and updated ds90ux9xx_get_link_status() function to core driver,
* added fpd_link_show device attribute.

Sandeep Jain added support of pixel clock edge configuration.

Signed-off-by: Vladimir Zapolskiy <redacted>
---
 drivers/mfd/Kconfig           |  14 +
 drivers/mfd/Makefile          |   1 +
 drivers/mfd/ds90ux9xx-core.c  | 879 ++++++++++++++++++++++++++++++++++
 include/linux/mfd/ds90ux9xx.h |  42 ++
 4 files changed, 936 insertions(+)
 create mode 100644 drivers/mfd/ds90ux9xx-core.c
 create mode 100644 include/linux/mfd/ds90ux9xx.h

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 8c5dfdce4326..a969fa123f64 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig

@@ -1280,6 +1280,20 @@ config MFD_DM355EVM_MSP
 	  boards.  MSP430 firmware manages resets and power sequencing,
 	  inputs from buttons and the IR remote, LEDs, an RTC, and more.
 
+config MFD_DS90UX9XX
+	tristate "TI DS90Ux9xx FPD-Link de-/serializer driver"
+	depends on I2C && OF
+	select MFD_CORE
+	select REGMAP_I2C
+	help
+	  Say yes here to enable support for TI DS90UX9XX de-/serializer ICs.
+
+	  This driver provides basic support for setting up the de-/serializer
+	  chips. Additional functionalities like connection handling to
+	  remote de-/serializers, I2C bridging, pin multiplexing, GPIO
+	  controller and so on are provided by separate drivers and should
+	  enabled individually.