bootstd: doc: Add documentation

Add documentation for this feature, including the commands and full
devicetree bindings.

Signed-off-by: Simon Glass <sjg@chromium.org>

doc/usage/cmd/bootmeth.rst

@@ -0,0 +1,108 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+bootmeth command
+================
+
+Synopis
+-------
+
+::
+
+    bootmeth list [-a]          - list selected bootmeths (-a for all)
+    bootmeth order "[<bm> ...]" - select the order of bootmeths\n"
+
+
+Description
+-----------
+
+The `bootmeth` command is used to manage bootmeths. It can list them and change
+the order in which they are used.
+
+See :doc:`../../develop/bootstd` for more information.
+
+
+.. _bootmeth_order:
+
+bootmeth order
+~~~~~~~~~~~~~~
+
+Selects which bootmeths to use and the order in which they are invoked. When
+scanning bootdevs, each bootmeth is tried in turn to see if it can find a valid
+bootflow. You can use this command to adjust the order or even to omit some
+boomeths.
+
+The argument is a quoted list of bootmeths to use, by name.
+
+
+bootmeth list
+~~~~~~~~~~~~~
+
+This lists the selected bootmeths, or all of them, if the `-a` flag is used.
+The format looks like this:
+
+=====  ===  ==================  =================================
+Order  Seq  Name                Description
+=====  ===  ==================  =================================
+    0    0  distro              Syslinux boot from a block device
+    1    1  efi                 EFI boot from an .efi file
+    2    2  pxe                 PXE boot from a network device
+    3    3  sandbox             Sandbox boot for testing
+    4    4  efi_mgr             EFI bootmgr flow
+=====  ===  ==================  =================================
+
+The fields are as follows:
+
+Order:
+    The order in which these bootmeths are invoked for each bootdev. If this
+    shows as a hyphen, then the bootmeth is not in the current ordering.
+
+Seq:
+    The sequence number of the bootmeth, i.e. the normal ordering if none is set
+
+Name:
+    Name of the bootmeth
+
+Description:
+    A friendly description for the bootmeth
+
+
+Example
+-------
+
+This shows listing bootmeths. All are present and in the normal order::
+
+    => bootmeth list
+    Order  Seq  Name                Description
+    -----  ---  ------------------  ------------------
+        0    0  distro              Syslinux boot from a block device
+        1    1  efi                 EFI boot from an .efi file
+        2    2  pxe                 PXE boot from a network device
+        3    3  sandbox             Sandbox boot for testing
+        4    4  efi_mgr             EFI bootmgr flow
+    -----  ---  ------------------  ------------------
+    (5 bootmeths)
+
+Now the order is changed, to include only two of them::
+
+    => bootmeth order "sandbox distro"
+    => bootmeth list
+    Order  Seq  Name                Description
+    -----  ---  ------------------  ------------------
+        0    3  sandbox             Sandbox boot for testing
+        1    0  distro              Syslinux boot from a block device
+    -----  ---  ------------------  ------------------
+    (2 bootmeths)
+
+The -a flag shows all bootmeths so you can clearly see which ones are used and
+which are not::
+
+    => bootmeth list -a
+    Order  Seq  Name                Description
+    -----  ---  ------------------  ------------------
+        1    0  distro              Syslinux boot from a block device
+        -    1  efi                 EFI boot from an .efi file
+        -    2  pxe                 PXE boot from a network device
+        0    3  sandbox             Sandbox boot for testing
+        -    4  efi_mgr             EFI bootmgr flow
+    -----  ---  ------------------  ------------------
+    (5 bootmeths)