Have a project that uses kernels built from kernel.org source.
Has worked fine with kernels up to 5.14.9, but have issues with 5.15.rc?
Works fine with syslinux, grub4dos, and grub2 booting with 5.14.9.
With 5.15.rc3 the kernel works in all situations, but video is totally distorted in others.
With syslinux boot, it works in boot with standard 640x480 resolution.
With the 5.14.9 can use the vga=ask, and can select other resolutions like 315 for 800x600, but the 5.15.rc3 gives distorted video that is compressed at top and duplicated across screen?
Similar with booting under grub4dos using standard USB boot.
With UEFI booting via grub2, even the default booting results with distorted video.
With the 5.14.9, the default boot, and options with vga=ask allow for correct video output.

Note the following changes to the .config file after copying the .config from the 5.14.9 build to the 5.15.rc3 build. Prompts for a number of changes, and select the default for options. Compare the .config files and find the following changes.
Lines with < are lines that were in 5.14.9, but not in 5.15.rc3 file?
Lines with NEW are lines that are added to the 5.15.rc3.

< CONFIG_PRINTK_NMI=y
NEW CONFIG_ARCH_NR_GPIO=1024
NEW CONFIG_PERF_EVENTS_AMD_UNCORE=y
< CONFIG_X86_SYSFB=y
NEW CONFIG_SYSFB=y
NEW CONFIG_TRACE_IRQFLAGS_SUPPORT=y
NEW CONFIG_ARCH_HAS_PARANOID_L1D_FLUSH=y
< CONFIG_BLK_SCSI_REQUEST=y
< CONFIG_BLK_DEV_BSG=y
NEW CONFIG_BLK_DEV_BSG_COMMON=y
< CONFIG_BLK_CMDLINE_PARSER=y
NEW CONFIG_BLOCK_HOLDER_DEPRECATED=y
NEW CONFIG_AF_UNIX_OOB=y
NEW CONFIG_SCSI_COMMON=y
NEW CONFIG_BLK_DEV_BSG=y
< CONFIG_CS89x0=y
< CONFIG_CS89x0_PLATFORM=y
NEW CONFIG_NET_VENDOR_LITEX=y
NEW CONFIG_PTP_1588_CLOCK_OPTIONAL=y
NEW CONFIG_INTEL_PUNIT_IPC=y
< CONFIG_INTEL_PUNIT_IPC=y
< CONFIG_MANDATORY_FILE_LOCKING=y
NEW CONFIG_SMBFS_COMMON=y
< CONFIG_CRYPTO_LIB_ARC4=y
< CONFIG_TRACE_IRQFLAGS_SUPPORT=y

The setups use the same  boot device, and same ramdisk.lzma, so only difference is the kernel. Never seen this before, and have been building kernels for project since 2004. Did just recently add the UEFI boot support, which added about 100 lines to the .config file to add framebuffers and fbcon. But that all works with the 5.14.x series of kernels. So, something in 5.15.rc is different?
Thanks for your time.