intel/intel_pmc_core: Add Intel PMC Core driver

[guest-seuros]

Summary

Add driver for Intel Power Management Controller (PMC) found on Sunrise Point PCH chipsets.
This device exposes S0ix sleep state residency counters and power management status.

Sysctls provided:

dev.intel_pmc_core.0.slp_s0_residency_us - Time in deepest sleep (us)
dev.intel_pmc_core.0.ltr_ignore          - LTR ignore mask
dev.intel_pmc_core.0.pm_cfg              - PM configuration register
dev.intel_pmc_core.0.pm_sts              - PM status register
dev.intel_pmc_core.0.access_denied       - Firmware lock status

Supported devices for now:

• Sunrise Point-LP (0x9D21)
• Sunrise Point-H (0xA121)

Note: Later PCH generations (Cannon Lake, Tiger Lake, ect.) have different PMC register layouts according to the datasheet and would need per-generation tables.
I avoided adding untested hardware in case they have a quirk.

[obiwac]

Cool that someone is working on an intel PMC driver!

I don't have time today to do a more in depth review, but here's a couple small comments already. I'll review this more fully this evening or tomorrow

sys/dev/intel/intel_pmc_core.c

2–16

The SPDX identifier should be the first line of the copyright header, and maybe make the driver description a separate comment to the copyright header.

Also if you want to you could add your name as such:

* This software was developed by Abdelkader Boudih <[e-mail]>
* under sponsorship from the FreeBSD Foundation.

92–103

a lot of this code could be factored out into a function which takes in oidp, req, and an offset, esp as we add sysctls for a bunch of the other registers.

175–178

I haven't read the docs yet so this might be a dumb question, but what is this register counting exactly? in theory a system using S0ix for suspend is always in S0. Or is this counting how much time the system is residing in _any_ S0ix state? perhaps the description could be updated if so.

[obiwac]

sys/dev/intel/intel_pmc_core.c

2–16

sorry, wrongly assumed you were working for the foundation.

You can just put your name straight in the copyright notice then:

/*
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2026 Abdelkader Boudih <[e-mail]>
 */

70–72

164–166

[guest-seuros]

Add files.x86 and modules entries; align slp_s0_residency sysctl name