ARM: Add STM32 family machine

STMicrolectronics's STM32 series is a family of Cortex-M
microcontrollers. It is used in various applications, and
proposes a wide range of peripherals.

Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/arm/stm32/overview.txt

@@ -0,0 +1,32 @@
+			STM32 ARM Linux Overview
+			========================
+
+Introduction
+------------
+
+  The STMicroelectronics family of Cortex-M based MCUs are supported by the
+  'STM32' platform of ARM Linux. Currently only the STM32F429 is supported.
+
+
+Configuration
+-------------
+
+  A generic configuration is provided for STM32 family, and can be used as the
+  default by
+	make stm32_defconfig
+
+Layout
+------
+
+  All the files for multiple machine families are located in the platform code
+  contained in arch/arm/mach-stm32
+
+  There is a generic board board-dt.c in the mach folder which support
+  Flattened Device Tree, which means, it works with any compatible board with
+  Device Trees.
+
+
+Document Author
+---------------
+
+  Maxime Coquelin <mcoquelin.stm32@gmail.com>