add mikoto_520 board back

Author: zhiayang

Diff for: app/boards/arm/mikoto/Kconfig

@@ -8,7 +8,7 @@ config BOARD_ENABLE_DCDC_HV
     bool "High voltage DCDC converter"
     select SOC_DCDC_NRF52X_HV
     default y
-    depends on (BOARD_MIKOTO_520)
+    depends on (BOARD_MIKOTO)
 
 choice BOARD_MIKOTO_CHARGER_CURRENT
     prompt "Charge current to supply to attached batteries"

Diff for: app/boards/arm/mikoto/mikoto_520.dts

@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "mikoto.dts"
+
+#include "mikoto-pinctrl.dtsi"
+#include "arduino_pro_micro_pins_v5.dtsi"
+

Diff for: app/boards/arm/mikoto/mikoto_520.yaml

@@ -0,0 +1,15 @@
+identifier: mikoto_520
+name: mikoto_520
+type: mcu
+arch: arm
+toolchain:
+  - zephyr
+  - gnuarmemb
+  - xtools
+supported:
+  - adc
+  - usb_device
+  - ble
+  - ieee802154
+  - pwm
+  - watchdog

Diff for: app/boards/arm/mikoto/mikoto_520.zmk.yml

@@ -0,0 +1,10 @@
+file_format: "1"
+id: mikoto_520
+name: Mikoto v5.20
+type: board
+arch: arm
+outputs:
+  - usb
+  - ble
+url: https://github.com/zhiayang/mikoto
+exposes: [pro_micro]

Diff for: app/boards/arm/mikoto/mikoto_520_defconfig

@@ -0,0 +1,26 @@
+# SPDX-License-Identifier: MIT
+# NOTE: copied from mikoto_defconfig
+
+CONFIG_SOC_SERIES_NRF52X=y
+CONFIG_SOC_NRF52840_QIAA=y
+CONFIG_BOARD_MIKOTO=y
+
+# Enable MPU
+CONFIG_ARM_MPU=y
+CONFIG_PINCTRL=y
+
+# enable GPIO
+CONFIG_GPIO=y
+
+CONFIG_USE_DT_CODE_PARTITION=y
+CONFIG_BUILD_OUTPUT_UF2=y
+
+CONFIG_MPU_ALLOW_FLASH_WRITE=y
+CONFIG_NVS=y
+CONFIG_SETTINGS_NVS=y
+CONFIG_FLASH=y
+CONFIG_FLASH_PAGE_LAYOUT=y
+CONFIG_FLASH_MAP=y
+
+CONFIG_ZMK_USB=y
+CONFIG_ZMK_BLE=y