doc: STM32 platform release notes (2025-11-13 – 2026-03-25)

[Copilot]

Adds a curated STM32 release note covering 382 merged PRs (label:"platform: STM32" merged:2025-11-13..2026-03-25) from the upstream zephyrproject-rtos/zephyr repository.

Changes

• doc/release-notes-stm32.rst – New RST document, organized by functional area:

  • New SoC/series: STM32C5 (full peripheral bring-up), STM32WBA2X, STM32H5E/F, STM32U3, STM32MP215F-DK, STM32MP13
  • New/updated boards: nucleo_u3c5zi_q, stm32f469i_disco AU1, stm32l4r9i DSI, stm32h7s78_dk, stm32n6570_dk, stm32h573i_dk, and others
  • Bluetooth & 802.15.4: STM32WBAx BLE/802.15.4 concurrent mode, disable support, OpenThread config, HAL updates (CubeWBA 1.8/1.9)
  • USB: isochronous endpoint support, multi-instance UDC, SOF, PHY/power refactoring
  • Drivers: ADC (RTIO/stream, resolution rework, injected channels), SPI (async DMA, RTIO, FIFO, extended data sizes), DMA (burst length fixes), Flash (OTP driver, WBA65 unaligned writes, XSPI improvements), Ethernet (H5/H7RS DWMAC, port selection, MAC addr from DT), Video/LTDC/DCMIPP, CRC, MSPI/XSPI, CAN FDCAN timestamping, I2S/SAI, Watchdog, UART
  • SoC / system: GPIO+PINCTRL decoupling, iocell driver (H5), Clock/PLL reworks (F2/F4/F7, H5/U5 fractional), power supply via DT, VOS via DT, backup SRAM retention, STM32N6 TrustZone/RIF, STM32MP2 OpenAMP/I3C
  • HAL: hal_stm32 bumped for WBA, H7RS, L4/L5, N6, WBxx/WLxx; migrated to generic LL headers; ll_func_* → ll_*

• doc/release-notes.rst – Added release-notes-stm32 entry to the TOC.

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