How to get subfields for custom fields and timetracking fields via REST API in JIRA?

[sakshi.chauhan]

Hi,
I am having the create meta API response for custom fields and timetracking field eg.

custom field:

{
"customfield_10019": {
"required": false,
"schema": {
"type": "any",
"custom": "com.pyxis.greenhopper.jira:gh-lexo-rank",
"customId": 10019
},
"name": "Rank",
"key": "customfield_10019",
"hasDefaultValue": false,
"operations": [
"set"
]
}
}

timetracking:  

{
"timetracking": {
"required": false,
"schema": {
"type": "timetracking",
"system": "timetracking"
},
"name": "Time tracking",
"key": "timetracking",
"hasDefaultValue": false,
"operations": [
"set",
"edit"
]
}
}

But I really need the subfields for custom field and timetracking to create the issue so there is any way or API for getting subfields for custom and timetracking fields ?
eg. custom field with subfield: 

"customfield_10019": {
"value": "Stuff"
}

eg. timetracking

"timetracking": {
"remainingEstimate": "5",
"originalEstimate": "10"
}