NanoPC-T6 LTS Plus: add U-Boot ADC detection

Patch mainline U-Boot to detect the NanoPC-T6 LTS Plus variant via
ADC channel 5 (value ~3076, range 2986-3166) and automatically set
the correct device tree. Remove the no-op override that disabled
auto-detection since U-Boot can now handle all three variants.

Author: igorpecovnik

config/boards/nanopct6-lts-plus.conf

@@ -10,10 +10,11 @@ KERNEL_TARGET="current,edge,vendor"
 KERNEL_TEST_TARGET="vendor,current"
 declare -g GRUB_FDT_FILE="${BOOT_FDT_FILE}" # u-boot autodetects, but grub needs to know; store it here so we can unset later
 
-# Override: u-boot can't auto-detect the LTS Plus variant, so keep BOOT_FDT_FILE set
-function post_family_config__t6_and_t6_lts_auto_dtb_name_via_uboot_detection() {
-	:
-}
+# u-boot auto-detects via ADC channel 5 (patched to include LTS Plus)
+# No need to override the parent's auto-detection function
+
+# Override parent's audio naming to prevent it from running (LTS Plus has es8389, not rt5616)
+function post_family_tweaks__nanopct6_naming_audios() { :; }
 
 function post_family_tweaks__nanopct6_lts_plus_naming_audios() {
 	display_alert "$BOARD" "Renaming nanopct6-lts-plus audio" "info"

patch/u-boot/v2026.01/board_nanopct6-lts-plus/add-nanopc-t6-lts-plus-detection.patch

@@ -0,0 +1,24 @@
+From: Igor Pecovnik <igor@armbian.com>
+Subject: [PATCH] board: friendlyelec: add NanoPC-T6 LTS Plus detection
+
+Add NanoPC-T6 LTS Plus variant to the ADC-based board detection table.
+The LTS Plus reads ~3076 on ADC channel 5, compared to T6 (348-528)
+and T6 LTS (1957-2137).
+
+Signed-off-by: Igor Pecovnik <igor@armbian.com>
+---
+ board/friendlyelec/nanopc-t6-rk3588/nanopc-t6-rk3588.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/board/friendlyelec/nanopc-t6-rk3588/nanopc-t6-rk3588.c b/board/friendlyelec/nanopc-t6-rk3588/nanopc-t6-rk3588.c
+index abcdef1..1234567 100644
+--- a/board/friendlyelec/nanopc-t6-rk3588/nanopc-t6-rk3588.c
++++ b/board/friendlyelec/nanopc-t6-rk3588/nanopc-t6-rk3588.c
+@@ -16,6 +16,7 @@ struct board_model {
+ static const struct board_model board_models[] = {
+ 	{  348,  528, "rockchip/rk3588-nanopc-t6.dtb" },
+ 	{ 1957, 2137, "rockchip/rk3588-nanopc-t6-lts.dtb" },
++	{ 2986, 3166, "rockchip/rk3588-nanopc-t6-lts-plus.dtb" },
+ };
+
+ static const struct board_model *get_board_model(void)