doc: man-page for bootz command

Provide a man-page for the bootz command.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

doc/usage/cmd/bootz.rst

@@ -0,0 +1,66 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+bootz command
+=============
+
+Synopsis
+--------
+
+::
+
+    bootz [<addr> [<initrd>[:<size>]] [<fdt>]]
+
+Description
+-----------
+
+The bootz command is used to boot a Linux kernel in 'zImage' format.
+
+addr
+    address of kernel image, defaults to the value of the environment
+    variable $loadaddr.
+
+initrd
+    address of the initial RAM disk. Use '-' to boot a kernel with a device
+    tree but without an initial RAM disk.
+
+size
+    size of the initial RAM disk. This parameter must be specified for raw
+    initial RAM disks.
+
+fdt
+    address of the device tree.
+
+Example
+-------
+
+This is the boot log of an OrangePi PC board:
+
+::
+
+    => load mmc 0:2 $fdt_addr_r dtb
+    23093 bytes read in 7 ms (3.1 MiB/s)
+    => load mmc 0:2 $kernel_addr_r vmlinuz
+    5079552 bytes read in 215 ms (22.5 MiB/s)
+    => load mmc 0:2 $ramdisk_addr_r initrd.img
+    23854965 bytes read in 995 ms (22.9 MiB/s)
+    => bootz $kernel_addr_r $ramdisk_addr_r:$filesize $fdt_addr_r
+    Kernel image @ 0x42000000 [ 0x000000 - 0x4d8200 ]
+    ## Flattened Device Tree blob at 43000000
+       Booting using the fdt blob at 0x43000000
+    EHCI failed to shut down host controller.
+       Loading Ramdisk to 48940000, end 49ffff75 ... OK
+       Loading Device Tree to 48937000, end 4893fa34 ... OK
+
+    Starting kernel ...
+
+Configuration
+-------------
+
+The bootz command is only available if CONFIG_CMD_BOOTZ=y.
+
+Return value
+------------
+
+Normally this command does not return. If an error occurs, the return value $?
+is set to 1 (false). If the operating system returns to U-Boot, the system is
+reset.

doc/usage/index.rst

@@ -30,6 +30,7 @@ Shell commands
    cmd/bootmenu
    cmd/bootmeth
    cmd/button
+   cmd/bootz
    cmd/cbsysinfo
    cmd/conitrace
    cmd/echo