Prepwork for non-PCIe NHI/TBT hosts

Currently, the NHI driver (and other parts of the TBT framework) make
multiple assumptions about the host router being a PCIe device. This
series tries to decouple them by moving the 'struct pci_device' out of
the NHI code and introduce NHI-on-PCIe-specific abstractions where
necessary (with no functional change).

The intended usage of the new nhi_probe_common() is pretty similar to
other bus frameworks (I2C, SPI, USB..), i.e.:

static int foo_bar_probe() {
        // get SoC-specifc resources (clks, regulators..)

        // power things on

        // set some implementation-specific registers

        // register NHI and all the sub-devices
        ret = nhi_probe(&my_usb4->nhi)
        ...

        // cleanup boilerplate
}

Instead of the previously-suggested aux/fauxbus, the NHI device remains
the same 'struct dev' as the PCIe/platform/[...] device that provides
it. This is in line with some other buses and it makes things easier
from the PM perspective.

Tested on:
* Qualcomm X1E80100 CRD (OOT driver)
 * USB4 (Qualcomm controller)
 * Connected to a TBT3 ASUS ProArt 27 monitor
 * Parade PS8830 on-board retimer

Domain 0 Route 0: 0000:0000
Domain 0 Route 2: 0031:9000 ASUS-Display PA27AC

* Intel Coffee Lake NUC (NUC8i3BEK)
 * TBT3 (Alpine Ridge 2C 2016 controller)
 * Connected to a Dell TB16 dock (TBT active cable)
 * S3 + S2idle sleep

Domain 0 Route 0: 8086:6357 Intel Corporation NUC8BEB
Domain 0 Route 1: 00d4:b051 Dell Dell Thunderbolt Cable
Domain 0 Route 301: 00d4:b054 Dell Dell Thunderbolt Dock

* AMD Ryzen 7 PRO 7840U-based Lenovo ThinkPad T14s Gen 4
 * USB4 ("Pink Sardine" controller)
 * Connected to a Lenovo ThinkPad Thunderbolt 3 Dock
 * Parade PS8830 on-board retimer
 * Only S2idle is present on this platform

Domain 0 Route 0: 0000:0000
Domain 1 Route 0: 0000:0000
Domain 1 Route 2: 0108:1630 Lenovo ThinkPad Thunderbolt 3 Dock

Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
---
Changes in v5:
- Rebase atop thunderbolt.git/next and re-test on the NUC
- Link to v4: https://patch.msgid.link/20260515-topic-usb4_nonpcie_prep...

Changes in v4:
- Fold in Icelake support to pci.c to avoid exporting nhi_pci_xx()
  functions and nhi_pci_ops
- I only compile-tested this revision, since it's a purely mechanical
  moving-around of code
- Link to v3: https://patch.msgid.link/20260513-topic-usb4_nonpcie_prep...

Changes in v3:
- Add missing/update affected kerneldoc
- Apply naming change suggestions
- Back out of moving tb_apple_add_links()
- Drop error log from nhi_pci_probe() calling nhi_probe()
- Unbreak some lines, touch up some change-adjacent whitespace
- Rebase on next-20260508
- Link to v2: https://lore.kernel.org/r/20260428-topic-usb4_nonpcie_pre...

Changes in v2:
- Make 'struct tb_nhi_pci' private, strip it of the 'struct pci_dev
  field since it can be accessed via to_pci_dev(tb_nhi_pci->nhi.dev)
- Thin out patch 1, move some of its prior contents to patch 2
- Rename nhi_pci.[ch] to pci.[ch]
- Rename nhi_probe_common() to nhi_probe()
- Squash a number of bugs discovered at runtime on x86
- Add a patch to make ops necessary to drop boilerplate checks
- Reword the error messages introduced in the last patch
- Drop RFC/RFT tags
- Link to v1: https://lore.kernel.org/r/20260309-topic-usb4_nonpcie_pre...

To: Andreas Noever <andreas.noever@gmail.com>
To: Mika Westerberg <westeri@kernel.org>
To: Yehezkel Bernat <YehezkelShB@gmail.com>
Cc: linux-usb@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

---
Konrad Dybcio (4):
      thunderbolt: Move pci_device out of tb_nhi
      thunderbolt: Separate out common NHI bits
      thunderbolt: Require nhi->ops be valid
      thunderbolt: Add some more descriptive probe error messages

 drivers/thunderbolt/Makefile    |   2 +-
 drivers/thunderbolt/acpi.c      |  14 +-
 drivers/thunderbolt/ctl.c       |  16 +-
 drivers/thunderbolt/domain.c    |   2 +-
 drivers/thunderbolt/eeprom.c    |   2 +-
 drivers/thunderbolt/icm.c       |  24 +-
 drivers/thunderbolt/nhi.c       | 520 ++++++---------------------------
 drivers/thunderbolt/nhi.h       |  33 ++-
 drivers/thunderbolt/nhi_ops.c   | 185 ------------
 drivers/thunderbolt/pci.c       | 622 ++++++++++++++++++++++++++++++++++++++++
 drivers/thunderbolt/switch.c    |  41 +--
 drivers/thunderbolt/tb.c        |  18 +-
 drivers/thunderbolt/tb.h        |  10 +-
 drivers/thunderbolt/usb4_port.c |   2 +-
 include/linux/thunderbolt.h     |   8 +-
 15 files changed, 805 insertions(+), 694 deletions(-)
---
base-commit: e24f3c0df48378214d9a67c5048d0faca144b163
change-id: 20260309-topic-usb4_nonpcie_prepwork-86881f769b8f

Best regards,
--  
Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>