add rpi5 custom example

board/raspberrypi5_custom/config.txt

@@ -0,0 +1,26 @@
+# See http://buildroot.org/manual.html#rootfs-custom
+# and http://elinux.org/RPiconfig for a description of config.txt syntax
+
+kernel=Image
+
+# To use an external initramfs file
+#initramfs rootfs.cpio.gz
+
+# Disable HDMI to reduce noise
+hdmi_ignore_hotplug=1
+hdmi_blanking=2
+disable_splash=1
+
+# gpu mem config (seems to be totally nececcarry - smaller than 32m does not boot on rpi3)
+gpu_mem=32
+
+# uart debug enable on GPIO14/15
+enable_uart=1
+uart_2ndstage=1
+dtparam=uart0_console
+dtdebug=1
+
+dtoverlay=disable-bt
+dtoverlay=disable-wifi
+dtoverlay=uart1-pi5
+dtoverlay=uart2-pi5