Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

This is required for FDT's standard "reg-io-width" property
(similar to "reg-shift" property) found in many DTS files.

This fixes operation on Altera Arria 10 SOC Development Kit,
where standard ns8250 uart allows 4-byte access only.

Reviewed by:	kan, marcel
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D9785

This is needed with the pl011 driver. Before this change it would default
to a shift of 0, however the hardware places the registers at 4-byte
addresses meaning the value should be 2.

This patch fixes this for the pl011 when configured using the fdt. The
other drivers have a default value of 0 to keep this a no-op.

MFC after:	1 week

console, it calls the grab functions. These functions should turn off
the RX interrupts, and any others that interfere. This makes mountroot
prompt work again. If there's more generalized need other than
prompting, many of these routines should be expanded to do those new
things.

Should have been part of r260889, but waasn't due to command line typo.

Reviewed by:	bde (with reservations)

clients. Mask RX interrupts while grabbed on the atmel serial
driver. This UART interrupts every character. When interrupts are
enabled at the mountroot> prompt, this means the ISR eats the
characters. Rather than try to create a cooperative buffering system
for the low level kernel console, instead just mask out the ISR. For
NS8250 and decsendents this isn't needed, since interrupts only happen
after 14 or more characters (depending on the fifo settings). Plumb
such that these are optional so there's no change in behavior for all
the other UART clients. ddb worked on this platform because all
interrupts were disabled while it was running, so this problem wasn't
noticed. The mountroot> issue has been around for a very very long
time.

MFC after:	3 days

it obtained through the uart_class structure. This allows us
to declare the uart_class structure as weak and as such allows
us to reference it even when it's not compiled-in.
It also allows is to get the uart_ops structure by name, which
makes it possible to implement the dt tag handling in uart_getenv().
The side-effect of all this is that we're using the uart_class
structure more consistently which means that we now also have
access to the size of the bus space block needed by the hardware
when we map the bus space, eliminating any hardcoding.

  that can be used to check whether receive data is ready, i.e. whether
  the subsequent call of uart_poll() should return a char, and unlike
  uart_poll() doesn't actually receive data.
- Remove the device-specific implementations of uart_poll() and implement
  uart_poll() in terms of uart_getc() and the newly added uart_rxready()
  in order to minimize code duplication.
- In sunkbd(4) take advantage of uart_rxready() and use it to implement
  the polled mode part of sunkbd_check() so we don't need to buffer a
  potentially read char in the softc.
- Fix some mis-indentation in sunkbd_read_char().

Discussed with:	marcel

for a character to be received. Instead let getc() do any necesary
locking.