New port: Anbernic RG Nano

A bit of context, this device is a clone of the FunKey-S with a different form factor, hardware is mostly identical, the relevant difference is it has audio out (via usb-c, adapter to 3.5mm is included), this is the reason why the FunKey-SDK is needed for bulding.

This port is based on the old SDL 1.2 code because the device doesn't have SDL2 support. Alongside what was supported in the SDL 1.2 builds this port supports battery level, charging status and backlight control.

Change-Id: I7fcb85be62748644b667c0efebabf59d6e9c5ade

firmware/target/hosted/anbernic/power-rgnano.c

@@ -0,0 +1,41 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ *
+ * Copyright (C) 2025 Hairo R. Carela
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include <sys/types.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#include "system.h"
+#include "power-rgnano.h"
+#include "power.h"
+#include "panic.h"
+#include "sysfs.h"
+
+const char * const sysfs_bat_level =
+    "/sys/class/power_supply/axp20x-battery/capacity";
+
+unsigned int rgnano_power_get_battery_capacity(void)
+{
+    int battery_level;
+    sysfs_get_int(sysfs_bat_level, &battery_level);
+
+    return battery_level;
+}