feat(linux): add BeaglePlay U-Boot build instructions

BeaglePlay has custom defconfigs (am62x_beagleplay_a53_defconfig
and am62x_beagleplay_r5_defconfig) just like other community
boards already documented (e.g. BeagleBadge), so it should be
included in the build guide.

Signed-off-by: Yiyoung Liu <y-liu20@ti.com>

Author: maybe-yiyi

source/linux/Foundational_Components/U-Boot/BG-Build-K3.rst

@@ -286,6 +286,9 @@ All of these binaries are available in the SDK at :file:`<path to tisdk>/board-s
    |  AM62SIP SK   | ``am6254atl_evm_r5_defconfig``     | ``am6254atl_evm_r5_defconfig am62x_r5_usbdfu.config``    | ``am6254atl_evm_r5_defconfig am62x_r5_usbmsc.config``    |
    |               | ``am6254atl_evm_a53_defconfig``    | ``am6254atl_evm_a53_defconfig``                          | ``am6254atl_evm_a53_defconfig``                          |
    +---------------+------------------------------------+----------------------------------------------------------+----------------------------------------------------------+
+   |  BeaglePlay   | ``am62x_beagleplay_r5_defconfig``  | ``am62x_beagleplay_r5_defconfig am62x_r5_usbdfu.config`` | ``am62x_beagleplay_r5_defconfig am62x_r5_usbmsc.config`` |
+   |               | ``am62x_beagleplay_a53_defconfig`` | ``am62x_beagleplay_a53_defconfig``                       | ``am62x_beagleplay_a53_defconfig``                       |
+   +---------------+------------------------------------+----------------------------------------------------------+----------------------------------------------------------+
 
    .. note::
 
@@ -346,6 +349,18 @@ All of these binaries are available in the SDK at :file:`<path to tisdk>/board-s
       $ make ARCH=arm CROSS_COMPILE="$CROSS_COMPILE_64" am6254atl_evm_a53_defconfig O=$UBOOT_DIR/out/a53
       $ make ARCH=arm CROSS_COMPILE="$CROSS_COMPILE_64" CC="$CC_64" BL31=$TFA_DIR/build/k3/lite/release/bl31.bin TEE=$OPTEE_DIR/out/arm-plat-k3/core/tee-pager_v2.bin O=$UBOOT_DIR/out/a53 BINMAN_INDIRS=$TI_LINUX_FW_DIR
 
+   .. rubric:: BeaglePlay
+
+   .. code-block:: console
+
+      R5
+      $ make ARCH=arm CROSS_COMPILE="$CROSS_COMPILE_32" am62x_beagleplay_r5_defconfig O=$UBOOT_DIR/out/r5
+      $ make ARCH=arm CROSS_COMPILE="$CROSS_COMPILE_32" O=$UBOOT_DIR/out/r5 BINMAN_INDIRS=$TI_LINUX_FW_DIR
+
+      A53
+      $ make ARCH=arm CROSS_COMPILE="$CROSS_COMPILE_64" am62x_beagleplay_a53_defconfig O=$UBOOT_DIR/out/a53
+      $ make ARCH=arm CROSS_COMPILE="$CROSS_COMPILE_64" CC="$CC_64" BL31=$TFA_DIR/build/k3/lite/release/bl31.bin TEE=$OPTEE_DIR/out/arm-plat-k3/core/tee-pager_v2.bin O=$UBOOT_DIR/out/a53 BINMAN_INDIRS=$TI_LINUX_FW_DIR
+
 
 .. ifconfig:: CONFIG_part_variant in ('AM62AX')