docs: arm: stm32: introduce STM32MP13 SoCs

STM32MP13 SoCs are derivative of STM32MP15 SoCs. They embed one Cortex-A7
plus standard connectivity.
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

Documentation/arm/index.rst

@@ -55,6 +55,7 @@ SoC-specific documents
    stm32/stm32h750-overview
    stm32/stm32f769-overview
    stm32/stm32f429-overview
+   stm32/stm32mp13-overview
    stm32/stm32mp157-overview
 
    sunxi

Documentation/arm/stm32/stm32mp13-overview.rst

+===================
+STM32MP13 Overview
+===================
+
+Introduction
+------------
+
+The STM32MP131/STM32MP133/STM32MP135 are Cortex-A MPU aimed at various applications.
+They feature:
+
+- One Cortex-A7 application core
+- Standard memories interface support
+- Standard connectivity, widely inherited from the STM32 MCU family
+- Comprehensive security support
+
+More details:
+
+- Cortex-A7 core running up to @900MHz
+- FMC controller to connect SDRAM, NOR and NAND memories
+- QSPI
+- SD/MMC/SDIO support
+- 2*Ethernet controller
+- CAN
+- ADC/DAC
+- USB EHCI/OHCI controllers
+- USB OTG
+- I2C, SPI, CAN busses support
+- Several general purpose timers
+- Serial Audio interface
+- LCD controller
+- DCMIPP
+- SPDIFRX
+- DFSDM
+
+:Authors:
+
+- Alexandre Torgue <alexandre.torgue@foss.st.com>