stm32: add minimal stm32wlex5 / lorae5 target

credit to ofauchon

src/machine/board_lorae5.go

@@ -0,0 +1,54 @@
+//go:build lorae5
+// +build lorae5
+
+package machine
+
+import (
+	"device/stm32"
+	"runtime/interrupt"
+)
+
+const (
+	LED1 = PB5
+	LED  = LED1 // Default LED
+)
+
+// SubGhz (SPI3)
+const (
+	SPI0_NSS_PIN = PA4
+	SPI0_SCK_PIN = PA5
+	SPI0_SDO_PIN = PA6
+	SPI0_SDI_PIN = PA7
+)
+
+// UARTS
+const (
+	//MCU USART1
+	UART1_TX_PIN = PB6
+	UART1_RX_PIN = PB7
+
+	//MCU USART2
+	UART2_TX_PIN = PA2
+	UART2_RX_PIN = PA3
+
+	// DEFAULT USART
+	UART_TX_PIN = UART1_TX_PIN
+	UART_RX_PIN = UART1_RX_PIN
+)
+
+var (
+	// Console UART
+	UART0  = &_UART0
+	_UART0 = UART{
+		Buffer:            NewRingBuffer(),
+		Bus:               stm32.USART1,
+		TxAltFuncSelector: AF7_USART1_2,
+		RxAltFuncSelector: AF7_USART1_2,
+	}
+	DefaultUART = UART0
+)
+
+func init() {
+	// Enable UARTs Interrupts
+	UART0.Interrupt = interrupt.New(stm32.IRQ_USART1, _UART0.handleInterrupt)
+}