doc: Bring in the FIT examples

Convert these to rST format and add them to the index.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/fit/update_uboot.rst b/doc/usage/fit/update_uboot.rst
new file mode 100644
index 0000000..a9288ee
--- /dev/null
+++ b/doc/usage/fit/update_uboot.rst
@@ -0,0 +1,28 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Automatic software update
+=========================
+
+Make sure the flashing addresses ('load' prop) is correct for your board!
+
+::
+
+    /dts-v1/;
+
+    / {
+        description = "Automatic U-Boot update";
+        #address-cells = <1>;
+
+        images {
+            update-1 {
+                description = "U-Boot binary";
+                data = /incbin/("./u-boot.bin");
+                compression = "none";
+                type = "firmware";
+                load = <0xFFFC0000>;
+                hash-1 {
+                    algo = "sha1";
+                };
+            };
+        };
+    };