Initial work on Proton-C board definition.

app/boards/arm/proton_c/proton_c_defconfig

@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: MIT
+
+CONFIG_SOC_SERIES_STM32F3X=y
+CONFIG_SOC_STM32F303XC=y
+# 72MHz system clock
+CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=72000000
+
+# Floating Point Options
+CONFIG_FPU=y
+
+# enable pinmux
+CONFIG_PINMUX=y
+
+# enable GPIO
+CONFIG_GPIO=y
+
+# clock configuration
+CONFIG_CLOCK_CONTROL=y
+
+# Clock configuration for Cube Clock control driver
+CONFIG_CLOCK_STM32_HSE_CLOCK=8000000
+CONFIG_CLOCK_STM32_SYSCLK_SRC_PLL=y
+# use HSE as PLL input
+CONFIG_CLOCK_STM32_PLL_SRC_HSE=y
+# produce 72MHz clock at PLL output
+CONFIG_CLOCK_STM32_PLL_PREDIV=1
+CONFIG_CLOCK_STM32_PLL_MULTIPLIER=9
+CONFIG_CLOCK_STM32_AHB_PRESCALER=1
+CONFIG_CLOCK_STM32_APB1_PRESCALER=2
+CONFIG_CLOCK_STM32_APB2_PRESCALER=1