[Xperia Z5 General] threader:
Found a great way to debug a kernel, using the -serial stdio flag of qemu.

qemu-system-aarch64 -m 2G -M virt -cpu cortex-a57 -kernel kernel-3.10.108/arch/arm64/boot/Image -append "console=ttyAMA0" -serial stdio

I compiled the kernel to arm64 defconfig. ish, as to not include device specific code, hopefully. In my case I found a Makefile in power/qemu that gracefully included the specific pm-boot.c, and other interesting stuff when compiling a different path.

Initializing cgroup subsys cpu
Linux version 3.10.108+ (thread@flappy) (gcc version 6.5.0 (Linaro GCC 6.5-2018.12~dev) ) #16 SMP PREEMPT Sun Aug 4 21:21:37 BST 2019
CPU: AArch64 Processor [411fd070] revision 0
Machine: linux,dummy-virt
cma: CMA: reserved 16 MiB at 0x00000000bf000000 for default region
psci: probing for conduit method from DT.
psci: Using PSCI v0.1 Function IDs from DT
PERCPU: Embedded 14 pages/cpu @ffffffc07efd1000 s27584 r8192 d21568 u57344
Built 1 zonelists in Zone order, mobility grouping on. Total pages: 517120
Kernel command line: console=ttyAMA0
PID hash table entries: 4096 (order: 3, 32768 bytes)
Dentry cache hash table entries: 262144 (order: 9, 2097152 bytes)
Inode-cache hash table entries: 131072 (order: 8, 1048576 bytes)
software IO TLB [mem 0xbcf00000-0xbd000000] (1MB) mapped at [ffffffc07cf00000-ffffffc07cffffff]
Memory: 2026012K/2097152K available (3600K kernel code, 281K rwdata, 1432K rodata, 214K init, 218K bss, 71140K reserved)
Virtual kernel memory layout:
vmalloc : 0xffffff8000000000 - 0xffffffbbffff0000 (245759 MB)
vmemmap : 0xffffffbc00e00000 - 0xffffffbc02a00000 ( 28 MB)
modules : 0xffffffbffc000000 - 0xffffffc000000000 ( 64 MB)
memory : 0xffffffc000000000 - 0xffffffc080000000 ( 2048 MB)
.init : 0xffffffc00056c000 - 0xffffffc0005a1bc0 ( 215 kB)
.text : 0xffffffc000080000 - 0xffffffc00056b094 ( 5037 kB)
.data : 0xffffffc0005a2000 - 0xffffffc0005e8738 ( 282 kB)
SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
Preemptible hierarchical RCU implementation.
RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=1.
NR_IRQS:64 nr_irqs:64 0
GIC CPU mask not found - kernel will fail to boot.
GIC CPU mask not found - kernel will fail to boot.
Architected cp15 timer(s) running at 62.50MHz (virt).
sched_clock: 56 bits at 62MHz, resolution 16ns, wraps every 2199023255552ns
Console: colour dummy device 80x25
allocated 8388608 bytes of page_cgroup
please try 'cgroup_disable=memory' option if you don't want memory cgroups
Calibrating delay loop (skipped), value calculated using timer frequency.. 125.00 BogoMIPS (lpj=625000)
pid_max: default: 32768 minimum: 301
Security Framework initialized
Mount-cache hash table entries: 256
Initializing cgroup subsys memory
Initializing cgroup subsys hugetlb
/cpus/cpu@0: Missing clock-frequency property
hw perfevents: no hardware support available
ASID allocator initialised with 65536 entries
Brought up 1 CPUs
SMP: Total of 1 processors activated.
devtmpfs: initialized
regulator-dummy: no parameters
NET: Registered protocol family 16
DMA: preallocated 256 KiB pool for atomic allocations
vdso: 2 pages (1 code, 1 data) at base ffffffc000404000
Serial: AMBA PL011 UART driver
9000000.pl011: ttyAMA0 at MMIO 0x9000000 (irq = 33) is a PL011 rev1
console [ttyAMA0] enabled
bio: create slab <bio-0> at 0
SCSI subsystem initialized
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
Switching to clocksource arch_sys_counter
NET: Registered protocol family 2
TCP established hash table entries: 16384 (order: 6, 262144 bytes)
TCP bind hash table entries: 16384 (order: 6, 262144 bytes)
TCP: Hash tables configured (established 16384 bind 16384)
TCP: reno registered
UDP hash table entries: 1024 (order: 3, 32768 bytes)
UDP-Lite hash table entries: 1024 (order: 3, 32768 bytes)
NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
Unpacking initramfs...
Freeing initrd memory: 14924K
kvm [1]: HYP mode not available
audit: initializing netlink socket (disabled)
type=2000 audit(0.990:1): initialized
error setting kswapd cpu affinity mask
HugeTLB registered 2 MB page size, pre-allocated 0 pages
fuse init (API version 7.23)
msgmni has been set to 4018
io scheduler noop registered
io scheduler row registered
io scheduler cfq registered (default)
Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
loop: module loaded
tun: Universal TUN/TAP device driver, 1.6
tun: (C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>
usbcore: registered new interface driver usb-storage
mousedev: PS/2 mouse device common for all mice
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
TCP: cubic registered
NET: Registered protocol family 17
registered taskstats version 1
regulator-dummy: disabling
VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
Please append a correct "root=" boot option; here are the available partitions:
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.10.108+ #3
Call trace:
[<ffffffc000087438>] dump_backtrace+0x0/0x108
[<ffffffc000087554>] show_stack+0x14/0x20
[<ffffffc000471fe0>] dump_stack+0x20/0x28
[<ffffffc00047114c>] panic+0xd8/0x224
[<ffffffc0005f8ce0>] mount_block_root+0x1b8/0x254
[<ffffffc0005f8e88>] mount_root+0x10c/0x128
[<ffffffc0005f8fd8>] prepare_namespace+0x134/0x17c
[<ffffffc0005f8978>] kernel_init_freeable+0x1c0/0x1e0
[<ffffffc00046c410>] kernel_init+0x18/0x128