Add bare-metal RK356x support for ROC-RK3566-PC, YY3568, and ROCK 3A

[hqnicolas]

Summary

Add bare-metal RK356x support for three explicitly described boards:

• Firefly ROC-RK3566-PC (roc3566)
• Youyeetoo YY3568 (yy3568)
• Radxa ROCK 3A (rock3a)

This follows the existing purpose and boot model of the project:

Rockchip BootROM
  -> vendor DDR initialization blob
  -> bare-metal rk firmware
  -> optional appended EL2 payload

Platform support

The shared src/rk356x/ platform adds:

• UART2 M0 at 1,500,000 baud
• RK356x PMU, CRU, GRF and SGRF setup
• DDR discovery using ATAGS, PMUGRF geometry, and a 1 GiB fallback
• RK356x-specific MMU and low-memory layout
• GPIO and board power control
• VOP2 and DW-HDMI initialization
• EDID-based progressive RGB modes through 4K30
• 720p60 fallback for unusable EDID
• Headless operation when HDMI HPD is absent
• USB2 PHY and polled OHCI support
• Directly attached HID boot-keyboard input
• FUEFI framebuffer, keyboard, memory-map, DTB and device-information services
• Reset and shutdown calls returning the SoC to MaskROM
• Existing appended-payload handoff at EL2

Board identity and wiring remain isolated in separate descriptors and minimal DTBs.

New artifacts

make all now produces:

ROC-RK3566-PC

• roc3566.bin
• demo_roc3566.bin
• roc3566.img
• demo_roc3566.img

YY3568

• yy3568.bin
• demo_yy3568.bin
• yy3568.img
• demo_yy3568.img

ROCK 3A

• rock3a.bin
• demo_rock3a.bin
• rock3a.img
• demo_rock3a.img

The SD images use the existing RKNS v2 packaging path.

USB loading

Explicit board-qualified loading targets were added:

make usb_roc3566
make usb_yy3568
make usb_rock3a

Optional SoC-level xrock USB-plug targets are also available:

make maskrom3566
make maskrom3568

rock.out recognizes Rockchip PID 0x350a as RK356x with RC4 disabled.

Rockchip binaries

Only the required RK356x binaries were added under img/:

• rk3566_ddr_1056MHz_v1.25.bin
• rk3568_ddr_1560MHz_v1.25.bin
• rk356x_usbplug_v1.17.bin

img/README.md records their pinned rkbin commit, original paths, sizes, SHA-256 hashes, and license provenance.

Existing-board compatibility

RK3399 and RK3588 retain their existing build commands and platform-specific object files.

RK356x objects use a separate .rk356x.o namespace and STACK_TOP=0x08000000, preventing RK356x memory-layout settings from leaking into other SoCs.

Shared firmware and demo changes are limited to:

• Dynamic framebuffer width, height and stride
• The existing FuScreenList.type field being defined as XRGB8888
• Functional keyboard FUEFI calls when a platform configures an input poller
• A freestanding memcmp() required by EDID parsing

Platforms without the new hooks retain their previous behavior.

Documentation

Added docs/rk356x/ with:

• A common RK356x bare-metal overview
• Memory layout and artifact documentation
• One wiring/status page for each supported board
• Direct MaskROM loading and SD demo instructions
• Explicit hardware-validation status

[hqnicolas]

chainloaders now live under https://github.com/hqnicolas/RK-SPI-NOR-Chainloader