[PATCH RFC 0/2] pinctrl: add syscon-backed packed-field pinctrl driver and DT bindings

[Billy Tsai <billy_tsai@aspeedtech.com>]

This work follows earlier review discussions around extending
pinctrl-single for bit-per-mux / packed-field controllers. Based on
feedback from Linus Walleij and Tony Lindgren, the direction was changed
towards introducing a separate targeted driver instead of further
increasing the complexity of pinctrl-single.

The prior pinctrl-single series is at:
https://lore.kernel.org/all/20260123-upstream_pinctrl_single-v2-0-40f8063cc5a2@aspeedtech.com/

This series is a replacement of that approach., targeted pinctrl driver
for controllers where pinmux and/or pin configuration are represented as
fixed-width fields packed sequentially within shared registers
(packed-field / bit-per-pin style controllers).

Although pinctrl-single contains support for some bit-per-mux use cases,
it was originally designed around direct MMIO ownership and has grown
in complexity over time. For SoCs where the pin controller lives inside
a larger SCU/syscon register block, using syscon + regmap-mmio provides
a clearer ownership model and naturally avoids MMIO resource conflicts.

The new driver is designed to be instantiated as a subnode of a syscon
device (e.g. SCU). It obtains a regmap from the parent and uses the
child node 'reg' as a window into the syscon register space.

This series includes:
  1. A generic Devicetree binding for packed-field pin controllers.
  2. The new pinctrl-packed driver (derived from pinctrl-single).

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
Billy Tsai (2):
      dt-bindings: pinctrl: Add pinctrl-packed
      pinctrl: add syscon-backed packed-field pin controller driver

 .../bindings/pinctrl/pinctrl-packed.yaml           |  166 +++
 drivers/pinctrl/Kconfig                            |   13 +
 drivers/pinctrl/Makefile                           |    1 +
 drivers/pinctrl/pinctrl-packed.c                   | 1168 ++++++++++++++++++++
 4 files changed, 1348 insertions(+)
---
base-commit: ea24857a76ad90632f86f1e8c8465f96c9f2e407
change-id: 20260211-pinctrl-single-bit-da213f282c95

Best regards,
-- 
Billy Tsai <billy_tsai@aspeedtech.com>