BR2_TARGET_GRUB2_CFG doesn't exist

As you know from make manuconfig "for additional notes on using Grub 2 with Buildroot, see boot/grub2/readme.txt" Inside this file you can find text

 6. Create a custom grub2 config file with the following contents and
    set its path in BR2_TARGET_GRUB2_CFG:

    set default="0"
    set timeout="5"

    menuentry "Buildroot" {
        set root='(hd0)'
        linux /boot/zImage root=/dev/mmcblk0 console=ttyAMA0
        devicetree /boot/vexpress-v2p-ca9.dtb
    }

But in buildroot there is no BR2_TARGET_GRUB2_CFG. There is BR2_TARGET_GRUB2_BUILTIN_CONFIG_PC but it is not the same because "menu entries cannot be described in this embedded configuration"

Looks like file boot/grub2/readme.txt should be fixed...