efi: doc: Add documentation for about efidebug boot

So far this subcommand is undocumented. Provide some notes.

Also show a better error when 'efidebug boot rm' fails.

Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/efidebug.c

@@ -1167,9 +1167,12 @@ static int do_efi_boot_rm(struct cmd_tbl *cmdtp, int flag,
 
 	guid = efi_global_variable_guid;
 	for (i = 1; i < argc; i++, argv++) {
-		id = (int)hextoul(argv[1], &endp);
-		if (*endp != '\0' || id > 0xffff)
+		id = (int)hextoul(argv[i], &endp);
+		if (*endp || id > 0xffff) {
+			printf("Invalid ID '%s', use '0001' for example\n",
+			       argv[i]);
 			return CMD_RET_FAILURE;
+		}
 
 		efi_create_indexed_name(var_name16, sizeof(var_name16),
 					"Boot", id);

doc/usage/cmd/efidebug.rst

@@ -13,6 +13,11 @@ Synopsis
 
 ::
 
+    efidebug boot add -b <bootid> <label> <interface> <devnum>[:<part>] <file>
+    efidebug boot rm <bootid> [<bootid> ...]
+    efidebug boot dump
+    efidebug boot next <bootid>
+    efidebug boot order [<bootid> ...]
     efidebug log
     efidebug media
     efidebug memmap [-s]
@@ -20,10 +25,44 @@ Synopsis
 Description
 -----------
 
-The *efidebug* command provides access to debugging features for the EFI-loader
-subsystem.
+The *efidebug* command provides access some EFI features, including boot
+management, memory mapping, and system information.
 
-Only three of the subcommands are documented at present.
+efidebug boot
+~~~~~~~~~~~~~
+
+The boot subcommands manage UEFI boot options (BootXXXX variables) and boot
+order.
+
+**efidebug boot add**
+    Create or modify a UEFI boot option. The basic syntax is:
+    ``efidebug boot add -b <bootid> <label> <interface> <devnum>[:<part>] <file>``
+
+    Where:
+
+    - ``<bootid>`` is a hexadecimal boot option ID (e.g., 0001, 000A)
+    - ``<label>`` is a descriptive name for the boot option
+    - ``<interface>`` is the storage interface (e.g., mmc, usb, virtio)
+    - ``<devnum>[:<part>]`` specifies device and optionally partition number
+    - ``<file>`` is the path to the EFI executable
+
+    Additional options include ``-i`` for initrd, ``-s`` for optional data,
+    and ``-d`` for device tree files.
+
+**efidebug boot rm**
+    Remove one or more UEFI boot options by their boot IDs.
+
+**efidebug boot dump**
+    List all defined UEFI boot options with their details including boot ID,
+    label, and file path.
+
+**efidebug boot next**
+    Set the BootNext variable to specify which boot option should be used for
+    the next boot only.
+
+**efidebug boot order**
+    Show the current boot order when called without arguments, or sets a new
+    boot order when given a list of boot IDs.
 
 efidebug log
 ~~~~~~~~~~~~
@@ -57,12 +96,38 @@ address, making it easier to visualize the memory layout in ascending order.
 Example
 -------
 
+This shows managing UEFI boot options::
+
+    => efidebug boot add -b 1 "Ubuntu" mmc 0:2 /EFI/ubuntu/grubx64.efi
+    => efidebug boot add -b 2 "Windows" mmc 0:1 /EFI/Microsoft/Boot/bootmgfw.efi
+    => efidebug boot dump
+    Boot0001:
+    attributes: A-- (0x00000001)
+    label: Ubuntu
+    file_path: /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/
+               HD(2,GPT,dfae5a37-e8d5-4a2e-aab6-6b6e8c8cb8a3,0x100800,
+               0x5dc1800)/\EFI\ubuntu\grubx64.efi
+    data: 
+    Boot0002:
+    attributes: A-- (0x00000001)
+    label: Windows
+    file_path: /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/
+               HD(1,GPT,c8a9e8e7-2d2a-4b8e-9b4f-7b7b3b7b7b7b,0x800,
+               0x100000)/\EFI\Microsoft\Boot\bootmgfw.efi
+    data:
+    => efidebug boot order 1 2
+    => efidebug boot order
+    BootOrder: 0001 0002
+    => efidebug boot next 2
+    => efidebug boot rm 1
+
 This shows checking the EFI media devices::
 
     => efidebug media
     Device               Media type       Device Path
     -------------------  ---------------  -----------
-    efi_media_1          ahci             PciRoot(0x0)/Pci(0x3,0x0)/Sata(0x0,0xFFFF,0x0)
+    efi_media_1          ahci             PciRoot(0x0)/Pci(0x3,0x0)/
+                                          Sata(0x0,0xFFFF,0x0)
     efi_media_2          pci              PciRoot(0x0)/Pci(0x5,0x0)
 
 This shows checking the UEFI memory map, first unsorted and then sorted by