Add new device in AOSP

I am beginner to AOSP, and trying to add new device in it for my learnings. So I am following below mentioned links new_device and new_device2

But when I compile it says "ninja: error: 'out/target/product/fp2/kernel', needed by 'out/target/product/fp2/boot.img', missing and no known rule to make it"

I have already tried to add TARGET_PREBUILT_KERNEL (for time being, given google-wahoo-kernel's prebuilt images).

NOTE added following files

1 . AndroidBoard.mk

LOCAL_PATH := device/fp/fp2/

TARGET_PREBUILT_KERNEL := $(LOCAL_PATH)/kernel

file := $(INSTALLED_KERNEL_TARGET)
ALL_PREBUILT += $(file)
$(file): $(TARGET_PREBUILT_KERNEL) | $(ACP)
$(transform-prebuilt-to-target)

#TARGET_PREBUILT_KERNEL=/home/campus/documents/workspace/project/fair_phone/src/android/device/google/wahoo-kernel/Image.lz4-dtb

2 . AndroidProducts.mk

PRODUCT_MAKEFILES := \
    $(LOCAL_DIR)/aosp_fp2.mk \

3 . aosp_fp2.mk

$(call inherit-product, $(SRC_TARGET_DIR)/product/core_64_bit.mk)
$(call inherit-product, $(SRC_TARGET_DIR)/product/aosp_base_telephony.mk)

PRODUCT_RESTRICT_VENDOR_FILES := owner

PRODUCT_MANUFACTURER := FairPhone
PRODUCT_BRAND := Android
PRODUCT_NAME := aosp_fp2
PRODUCT_DEVICE := fp2
PRODUCT_MODEL := AOSP on fp2

4 . BoardConfig.mk

DEVICE_PATH := device/fp/fp2

# Binder API version
TARGET_USES_64_BIT_BINDER := true

# Bootloader
TARGET_BOOTLOADER_BOARD_NAME := fp2
TARGET_NO_BOOTLOADER := false
TARGET_NO_RADIOIMAGE := true

# Platform
TARGET_BOARD_PLATFORM := msm8974

# Kernel
BOARD_KERNEL_BASE        := 0x00000000
BOARD_KERNEL_PAGESIZE    := 2048
BOARD_KERNEL_TAGS_OFFSET := 0x01E00000
BOARD_RAMDISK_OFFSET     := 0x02000000
TARGET_KERNEL_ARCH := arm
TARGET_KERNEL_CONFIG := lineageos_FP2_defconfig
TARGET_KERNEL_SOURCE := kernel/fairphone/msm8974
TARGET_KERNEL_CROSS_COMPILE_PREFIX := arm-linux-androideabi-
BOARD_KERNEL_CMDLINE := androidboot.hardware=qcom user_debug=31 msm_rtb.filter=0x3b7 ehci-hcd.park=3 androidboot.bootdevice=msm_sdcc.1
BOARD_KERNEL_SEPARATED_DT := true
BOARD_KERNEL_IMAGE_NAME := zImage

# Architecture
TARGET_ARCH := arm
TARGET_ARCH_VARIANT := armv7-a-neon
TARGET_CPU_ABI  := armeabi-v7a
TARGET_CPU_ABI2 := armeabi
TARGET_CPU_VARIANT := krait

# Filesystem
BOARD_BOOTIMAGE_PARTITION_SIZE := 0x01000000
BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4
BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := f2fs
BOARD_CACHEIMAGE_PARTITION_SIZE := 671088640
BOARD_FLASH_BLOCK_SIZE := 131072 # (BOARD_KERNEL_PAGESIZE * 64)
BOARD_PERSISTIMAGE_FILE_SYSTEM_TYPE := ext4
BOARD_PERSISTIMAGE_PARTITION_SIZE := 5242880
BOARD_RECOVERYIMAGE_PARTITION_SIZE := 0x01000000
BOARD_SYSTEMIMAGE_PARTITION_SIZE := 2147483648
BOARD_TOMBSTONESIMAGE_PARTITION_SIZE := 73400320
BOARD_USERDATAIMAGE_PARTITION_SIZE := 27358941675
TARGET_USERIMAGES_USE_EXT4 := true
TARGET_USERIMAGES_USE_F2FS := true

5 . vendorsetup.sh

add_lunch_combo aosp_fp2-userdebug

6 . device.mk

PRODUCT_HARDWARE := fp2

Error log is linked err_log_attachment

I have couple of questions

1 . it seems that build setup is not proper to compile kernel. If so, how to compile customized kernel in AOSP ?

2 . How configure git kernel source code ?

3 . How to use TARGET_PREBUILT_KERNEL ?

Thanks and regards, Pritam