how to put a host to a (just in parent) subdomain

[lejeczek]

hi everybody

I'm trying something simple, or I thought it'd be simple, I 
realize my question should rather go towards DHCPD 
community, but I feel like I might be missing something on 
DNS part.
for organizational, or for test if you like, purposes I 
would like to have

subdomain.inparent.zone (so no delegations, just in parent 
zone) - this works with nsupdate simply:

 > zone inparent.zone.
 > update add host.subdomain.inparent.zone 86400 in a 
10.10.1.10
 > send
$ host host.subdomain
and it resolves fine, and if I fix my resolv.conf 
respectively it even resolves host

is above correct and nothing else in terms of records & 
configs is required in order to add a subdomain to already 
existing parent?
and if so, would you know if it's hosts(dhcpd clients) that 
need specific configs or just DHCPd does the lot?
I should mention it's all dnssec.

many thanks.