Actually, have moved on a bit. Using static IPs and a crossover cable, it now starts to boot but gets stuck at port lookup, full transcript including back trace below:
U-Boot 1.1.6 (Feb 2 2010 - 17:29:26 - GCC 4.3.2) DUB-RevF4
for ConnectCore 9P 9215 on Development Board
DRAM: 32 MB
Flash: 16 MB
CPU: NS9215 @ 149.91360 MHz, SYS 299.82720 MHz, AHB 74.95680 MHz, Rev 0
Strap: 0x05f0
Autoscript from TFTP... [not available]
Hit any key to stop autoboot: 0
CC9P9215 # dboot linux tftp
TFTP from server 10.10.20.43; our IP address is 10.10.20.48
Filename 'uImage-cc9p9215js'.
Load address: 0x200000
Loading: #################################################################
#######################
done
Bytes transferred = 1250104 (131338 hex)
linux will be booted now
## Booting image at 00200000 ...
Image Name: Linux-2.6.35.14
Created: 2017-01-30 20:34:47 UTC
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 1250040 Bytes = 1.2 MB
Load Address: 00008000
Entry Point: 00008000
Verifying Checksum ... OK
fixing Load address and Entry Point: 00200040 00200040 ...
XIP Kernel Image ... OK
Starting kernel ...
Uncompressing Linux... done, booting the kernel.
Linux version 2.6.35.14 (dsb@dsb-ws1) (gcc version 4.4.6 (crosstool-NG 1.12.1) ) #1968 Mon Jan 30 15:34:43 EST 2017
CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00053177
CPU: VIVT data cache, VIVT instruction cache
Machine: ConnectCore 9P 9215 on a JSCC9P9215 Devboard
Memory policy: ECC disabled, Data cache writeback
Built 1 zonelists in Zone order, mobility grouping on. Total pages: 8128
Kernel command line: ip=10.10.20.48:10.10.20.43:10.10.20.1:255.255.255.0:cc9p9215js:eth0:off console=ttyNS3,38400 root=nfs nfsroot=10.10.20.43:/exports/nfsroot-cc9p9215js mtdparts=physmap-flash.0:0x40000(U-Boot),0x40000@0x40000(NVRAM),0)
PID hash table entries: 128 (order: -3, 512 bytes)
Dentry cache hash table entries: 4096 (order: 2, 16384 bytes)
Inode-cache hash table entries: 2048 (order: 1, 8192 bytes)
Memory: 32MB = 32MB total
Memory: 29920k/29920k available, 2848k reserved, 0K highmem
Virtual kernel memory layout:
vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xfff00000 - 0xfffe0000 ( 896 kB)
DMA : 0xffc00000 - 0xffe00000 ( 2 MB)
vmalloc : 0xc2800000 - 0xf0000000 ( 728 MB)
lowmem : 0xc0000000 - 0xc2000000 ( 32 MB)
modules : 0xbf000000 - 0xc0000000 ( 16 MB)
.init : 0xc0008000 - 0xc001f000 ( 92 kB)
.text : 0xc001f000 - 0xc025b000 (2288 kB)
.data : 0xc025c000 - 0xc026d480 ( 70 kB)
NR_IRQS:82
Calibrating delay loop... 74.13 BogoMIPS (lpj=370688)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
devtmpfs: initialized
NET: Registered protocol family 16
Inverting RTS
bio: create slab <bio-0> at 0
Switching to clocksource ns921x-timer0
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 1024 (order: 1, 8192 bytes)
TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
TCP: Hash tables configured (established 1024 bind 1024)
TCP reno registered
UDP hash table entries: 256 (order: 0, 4096 bytes)
UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
NET: Registered protocol family 1
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
JFFS2 version 2.2. (NAND) (SUMMARY) �© 2001-2006 Red Hat, Inc.
msgmni has been set to 58
io scheduler noop registered (default)
adc-ns9215: ADC available on MAJOR 253
ns921x-serial.0: ttyNS0 at MMIO 0x90010000 (irq = 7) is a NS921X PORT A
ns921x-serial.1: ttyNS1 at MMIO 0x90018000 (irq =

is a NS921X PORT B
ns921x-serial.2: ttyNS2 at MMIO 0x90020000 (irq = 9) is a NS921X PORT C
ns921x-serial.3: ttyNS3 at MMIO 0x90028000 (irq = 10) is a NS921X PORT D
console [ttyNS3] enabled
Digi NS921x UART driver
brd: module loaded
physmap platform flash device: 10000000 at 50000000
physmap-flash.0: Found 1 x16 devices at 0x0 in 16-bit bank
Amd/Fujitsu Extended Query Table at 0x0040
number of CFI chips: 1
4 cmdlinepart partitions found on MTD device physmap-flash.0
Creating 4 MTD partitions on "physmap-flash.0":
0x000000000000-0x000000040000 : "U-Boot"
0x000000040000-0x000000080000 : "NVRAM"
0x000000080000-0x000000200000 : "Kernel"
0x000000200000-0x000001000000 : "RootFS"
ns9xxx-eth-mii: probed
ns9xxx-eth ns9xxx-eth: eth0 at MMIO c285c000
Digi NS9XXX Ethernet driver
rtc-ns9xxx rtc-ns9xxx.0: rtc core: registered rtc-ns9xxx as rtc0
ns9xxx-wdt ns9xxx-wdt: NS9xxx watchdog timer at 0xc286e174
TCP cubic registered
NET: Registered protocol family 17
rtc-ns9xxx rtc-ns9xxx.0: hctosys: unable to read the hardware clock
IP-Config: Complete:
device=eth0, addr=10.10.20.48, mask=255.255.255.0, gw=10.10.20.1,
host=cc9p9215js, domain=, nis-domain=(none),
bootserver=10.10.20.43, rootserver=10.10.20.43, rootpath=
Looking up port of RPC 100003/2 on 10.10.20.43
net eth0: link up (100/full)
rpcbind: server 10.10.20.43 not responding, timed out
Root-NFS: Unable to get nfsd port number from server, using default
Looking up port of RPC 100005/1 on 10.10.20.43
rpcbind: server 10.10.20.43 not responding, timed out
Root-NFS: Unable to get mountd port number from server, using default
Root-NFS: Server returned error -110 while mounting /exports/nfsroot-cc9p9215js
VFS: Unable to mount root fs via NFS, trying floppy.
VFS: Cannot open root device "nfs" or unknown-block(2,0)
Please append a correct "root=" boot option; here are the available partitions:
1f00 256 mtdblock0 (driver?)
1f01 256 mtdblock1 (driver?)
1f02 1536 mtdblock2 (driver?)
1f03 14336 mtdblock3 (driver?)
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
Backtrace:
[<c0023028>] (dump_backtrace+0x0/0x114) from [<c01d14d8>] (dump_stack+0x18/0x1c)
r7:c0224ba8 r6:00008000 r5:c1c29000 r4:c026dad8
[<c01d14c0>] (dump_stack+0x0/0x1c) from [<c01d153c>] (panic+0x60/0xdc)
[<c01d14dc>] (panic+0x0/0xdc) from [<c0008fd8>] (mount_block_root+0x1d8/0x218)
r3:00000000 r2:00000000 r1:c1c17f60 r0:c0224c4f
[<c0008e00>] (mount_block_root+0x0/0x218) from [<c00090dc>] (mount_root+0xc4/0xfc)
[<c0009018>] (mount_root+0x0/0xfc) from [<c0009280>] (prepare_namespace+0x16c/0x1d0)
r5:c001ca24 r4:c026d740
[<c0009114>] (prepare_namespace+0x0/0x1d0) from [<c00084e8>] (kernel_init+0x118/0x158)
r5:c001b470 r4:c026d500
[<c00083d0>] (kernel_init+0x0/0x158) from [<c0031c64>] (do_exit+0x0/0x5f8)
r5:c00083d0 r4:00000000