RK3576: Enable USB-C DisplayPort Alt Mode output

[pgratz1]

Summary

• Add three kernel patches enabling DP Alt Mode on RK3576 via the DesignWare DP controller:
  • 0015: Fix RK3576 VOP2 VP2 — promote Esmart0 to PRIMARY plane and clear the VP2 pixel-clock divider for DP output
  • 0016: Add RK3576 to the dw-dp driver OF match table, make i2s/spdif clocks optional, and add single-pixel input mode for VP2
  • 0017: Add the DP controller node (dp@27e40000) to the RK3576 base DTSI
• Enable CONFIG_ROCKCHIP_DW_DP and CONFIG_TYPEC_DP_ALTMODE in the RK3576 kernel config
• Wire VP2 → DP0 output path in the RG Vita Pro device tree

Tested on ANBERNIC RG Vita Pro with VITURE Pro XR glasses at 1920×1080@60 Hz via USB-C.

This is a split of #2647 containing only the kernel/DTS portion, per reviewer request. Userspace display-switching scripts (dp_monitor, sway config) will follow in a separate PR once these patches are merged.

Test plan

• Build RK3576 image from this branch
• Flash to ANBERNIC RG Vita Pro
• Connect VITURE Pro XR glasses via USB-C — confirm DP-1 output initialises in sway at 1920×1080@60 Hz
• Disconnect glasses — confirm device continues to function normally on DSI-1

🤖 Generated with Claude Code

[pgratz1]

Tested on ANBERNIC RG Vita Pro with VITURE Pro XR glasses. The kernel patches are working — /sys/class/drm/card0-DP-1/status reports connected when the glasses are plugged in via USB-C. Sway can successfully output to DP-1 once directed there manually:

swaymsg output DP-1 enable
swaymsg "workspace 1 output DP-1 DSI-1"
swaymsg focus output DP-1 && foot &

After those commands a foot terminal appeared on the glasses at the correct resolution. Without them, sway routes nothing to DP-1 on its own — the automatic workspace routing and display-switching logic (dp_monitor) will follow in a separate PR.

[sydarn]

LGTM let's merge this :)

If this doesn't work at boot I would guess that's a bug in the 111-sway-init script. It's supposed to prioritize HDMI and DP if connected. Logic starting here:

distribution/projects/ROCKNIX/packages/wayland/compositor/sway/autostart/111-sway-init

Line 29 in 8e4055f

card_no=$(ls /sys/class/drm/ | grep -E "DP|HDMI|DSI" | head -n 1 | cut -b 5)