A driver for the NXP SC16IS7xx family of UART chips. This family is
mostly a 16C450 with features from the 16C550, 16C650 and 16C750 and
makes use of src/sys/dev/ic/com.c for much of the heavy lifting.

A BIG difference is that the chip family is attached via a I2C or SPI
bus and is in no way, shape or form, attached to the computer via a
computer bus.

Since spin locks are not allowed to be held while calling to the I2C
or SPI framework com.c grew a new hw feature flag where it could be
run at something other than a hard IP level and doesn't hold spin lock
(for very long). In particular, IPL_SOFTSERIAL. This method is
enabled via a hw feature flag and should not effect any other use of
com.c. Other changes with this new method of use include the use of
workqueues and such.

A further feature added to com.c was the abilty to take advantage of
the MCR prescaler that is present in the SC16IS7xx family and likely
present in the 16C650. This prescaler is tried if the baud rate
requested can not be met with the frequency oscillator that the chip is
built with.

The chip family does not use any particular frequency oscillator for
the baud rate generator. In order to deal with this the frequency can
be set via sysctl, a kernel option or with a FDT overlay if that is
supported.

Most of the features of the chip family are supported including the
gpio pins via gpiobus(4) that are present with some of the family
members.

The chip can attach via I2C or SPI and can make sure of FDT if that is
present in the system.

This chip family has been around for quite some time and there are a
number of breakout boards on Amazon. It is also reasonably priced and
you can roll your own board if you can perform simple SMD soldering as
very few additional components are required.

If using FDT, get Vref from the device tree per the documented bindings
for this device.

Step towards modularizing the Flattened Device Tree code.

Define attributes for each of the specific device bindings: clock,
dai, dma, gpio, i2c, iommu, mbox, mmc_pwrseq, phy, power, power domain,
pwm, regulator, reset controller, spi, system controller, pin
controller. Include these support files only if either a provider
or consumer with one of these attributes is present in the kernel
config.

Add the necessary attributes to the device / attach declarations for
each provider and consumer.

There are some bindings that are consumed by generic code (iommu, pinctrl,
power, power domain). Provide weak stubs for these routines to handle
situations where there is no provider.

No actual code changed; NFCI.

Split the BMP280 / BME280 driver into common code and create I2C and
SPI attachments.

Re-factor and overhaul the "mcp23s17gpio" driver as "mcpgpio", and
add support for 8-bit and I2C variants of the chip:
- MCP23008 / MCP23S08: 8-bit (I2C / SPI)
- MCP23017 / MCP23S17: 16-bit (I2C / SPI)
- MCP23018 / MCP23S18: 16-bit (I2C / SPI), open-drain outputs

The MCP23x17 and MCP23x18 are essentially identical, software-wise; we
merely report different GPIO pin capabilities (no push-pull output for
MCP23x18). Also, remove the tri-state capability that was previously
advertised by the old version of this driver; these chips have no way
to put the pin into a HI-Z mode.

All 3 I2C versions are supported, but the SPI front-end still only
supports the MCP23S17 for now (SPI autoconfiguration needs an overhaul).

mcp23s17gpio(4) remains present as a link to the new mcpgpio(4) man page.

XXX Still to-do: FDT integration, interrupt suppoort.

A driver and user land utility for the Sparkfun Serial Controlled Motor
Driver module as illustrated here:

https://www.sparkfun.com/products/13911

A SCMD module is a ARM SOC simular to a Arduino in front of a motor
driver chip. The single SCMD module can control two motors and up to
16 additional modules can be chained together using an internal I2C
bus. One can interface with the SCMD using tty uart commands, SPI or
I2C. The driver in this commit adds a kernel driver for the I2C and
SPI interfaces. The command line utility provides a set of
convenience commands that support most of the functions of the SCMD
and is able to use the tty uart mode, SPI user land or the included
kernel driver in a uniform manor.

The use of the SCMD module is mostly for small robots and the like,
but it can control anything that is controllable by voltage.

add spi(4) bus frontend for ssdfb(4)

spi: make the "slave" config(5) locator optional

needed to be able to support FDT direct attachment of SPI slaves

branches: 1.5.18;
MI driver for the Microchip 3x0x series of SAR analog to digital converters.

branches: 1.4.4;
add Microchip MCP23S17 GPIO driver
(via SPI interface)

branches: 1.3.2;
Add preliminary driver for Microchip MCP48x1 family of DACs.

Needs more testing and an appropriate API for such (non-audio) DACs. For now
one can set the output value using sysctl node. Also sysmon(4) will conveniently
report the voltage on Vout pin of the DAC. Note that this is not an actual
measured voltage, but merely calculated using equation from datasheet. Real
voltage might be different and depend on analog circuitry attached to the DAC.

branches: 1.2.2; 1.2.4; 1.2.8; 1.2.38; 1.2.94; 1.2.104; 1.2.110; 1.2.114;
Add spiflash driver, and M25P instance, used for STMicro flash devices
found on Meraki Mini (for example).

Initial commit of SPI bus (also known as Microwire) framework, along with
a sample driver for the TI TMP121 temperature sensor. This has been
moderately tested on Au1550, and it is not enabled in sys/conf (yet). So
the change is harmless at worst, and useful at best.

Alchemy Au1550 bus driver forthcoming, along with a driver for SPI flash
devices, such as found on the Meraki Mini

This development was partially funded by the Champaign-Urbana Community
Wireless Network Project.

Note that there are some MD-specific SPI drivers that could probably be
made MI under this new framework.