Backport of r338074 - generalize uart_bus_probe and add SNPS support to x86

Submitted by: Rajesh Kumar
Differential Revision: https://reviews.freebsd.org/D17381

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Replace mips/sentry5 with mips/broadcom

The delta between SENTRY5 and BCM was already small due to BCM being
derived from SENTRY5; re-integrating the two avoids the maintenance
overhead of keeping them both in sync with bhnd(4) changes.


- Re-integrate minor SENTRY5 deltas in bcm_machdep.c
- Modify uart_cpu_chipc to allow specifying UART debug/console flags via
kenv and device hints.
- Switch SENTRY5 to std.broadcom
- Enabled CFI flash support for SENTRY5

Reviewed by: Michael Zhilin <mizkha@gmail.com> (Broadcom MIPS support)
Approved by: re (gjb), adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6897

bhnd(4): Perform explicit chipc child enumeration.

Replaces use of DEVICE_IDENTIFY with explicit enumeration of chipc
child devices using the chipc capability structure.

This is a precursor to PMU support, which requires more complex resource
assignment handling than achievable with the static device name-based
hints table.

Reviewed by: Michael Zhilin <mizkha@gmail.com> (Broadcom MIPS support)
Approved by: re (gjb), adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6896

bhnd(4): Fix mips/broadcom core matching and bus pass order.

Changes:

- Fixed incorrect MIPS74k vendor ID in the bhnd core descriptor tables
- Fixed MIPS core driver's matching against MIPS/MIPS33 cores.
- Improved MIPS3302 core description.
- Enabled BUS_PASS_BUS on the bhnd nexus drivers to allow early probing
of the MIPS core.
- Enabled BUS_PASS_CPU on the MIPS core driver to ensure correct attach
order.
- Disabled matching of the MIPS core driver on non-SoC devices.

Reviewed by: Michael Zhilin <mizhka@gmail.com>
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6735

bhnd(4): Add a vendor parameter to BHND_DEVICE(), replacing vendor-specific
BHND_*_DEVICE macros.

Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6736

Switch mips/sentry5 to bhnd(4), and unify with mips/broadcom

Now that bhnd(4) provides feature parity with the previous siba/mips
implementation, we can switch sentry5 over and begin lifting common
support code out for use across bhnd(4) embedded targets.

Changes:

- Fixed enumeration of siba(4) per-core address maps, required for
discovery of memory mapped chipc flash region on siba(4) devices.
- Simplified bhnd kernel configuration (dropped 'bhndbus' option).
- Replaced files.broadcom's direct file references with their
corresponding standard kernel options.
- Lifted out common bcma/siba nexus support, inheriting from the new
generic bhnd_nexus driver.
- Dropped now-unused sentry5 siba code.
- Re-integrated BCM into the universe build now that it actually compiles.

Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6712

bhnd(4): Add support for chipc-attached flash

This adds support for serial (via SPI) and parallel (via CFI) flash
as found on BCM47xx/BCM53xx SoCs.

Submitted by: Michael Zhilin <mizhka@gmail.com>
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6250

[mips/broadcom] Add initial support for Broadcom MIPS processor

Relies on BHND(4) driver.

There files contains machine-dependent code for Broadcom MIPS processor and
provide UART driver.

This is a work in progress; it and the current bhnd code is enough to boot
on the ASUS RT-N16 and RT-N53 platforms.

Submitted by: Michael Zhilin <mizhka@gmail.com>
Differential Revision: https://reviews.freebsd.org/D6251

[mips/broadcom] Add initial code for interrupts on the Broadcom MIPS processor

Broadcom MIPS processor doesn't reset TI flag if additional manipulation
is done.

Thanks to @sobomax!