doc: board: Add missing board index.rst files
These board index.rst files are missing in previous html doc patch
series, hence it causes some build warnings. Add those files.
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/doc/board/xilinx/index.rst b/doc/board/xilinx/index.rst
new file mode 100644
index 0000000..2416fbd
--- /dev/null
+++ b/doc/board/xilinx/index.rst
@@ -0,0 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Xilinx
+======
+
+.. toctree::
+ :maxdepth: 2
+
+ zynq