tcl/board/orange_pi_zero_3: Add Orange Pi Zero 3 board

The Orange Pi Zero 3 is an SBC that uses an Allwinner H618
SoC. As such, JTAG support is fully available, however the
SoC multiplexes JTAG function with UART1 and microSD.
Unfortunately Xunlong has used UART1 for the Wifi-BT
chip, leaving JTAG accessible only via the microSD using
a microSD breakout board (for example).

Change-Id: I0dc078cd2f3176815271917eb5e948cc8ef94525
Signed-off-by: Electric Worry <me@electricworry.net>
Reviewed-on: https://review.openocd.org/c/openocd/+/8938
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>

tcl/board/orange_pi_zero_3.cfg

@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# This is the Orange Pi Zero 3 board with Allwinner H618 chip
+# http://www.orangepi.org/html/hardWare/computerAndMicrocontrollers/details/Orange-Pi-Zero-3.html
+#
+# Accessing JTAG signals on Orange Pi Zero 3 board requires connection to pins
+# on the microSD card slot.
+#   1 - DAT2    - TCK
+#   2 - CD/DAT3 - NC
+#   3 - CMD     - TDO
+#   4 - VDD     - NC
+#   5 - CLK     - NC
+#   6 - VSS     - NC
+#   7 - DAT0    - TDI
+#   8 - DAT1    - TMS
+#
+# PF Configure Register 0 at address 0x0300b0b4 must be set 0x07373733 to set
+# the JTAG function on these pins (which is what the factory installed image on
+# the SPI flash does when the board is powered without a microSD inserted).
+
+source [find target/allwinner_h618.cfg]
+
+# To this contributor's knowledge, the board neither exposes TRST nor SRST.
+reset_config none