deploy1.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: meow
  namespace: default
spec:
  template:
    spec:
      containers:
      - image: nginx
        name: nginx
        resources:
          requests:
            memory: "100Mi"
            cpu: "100m"
          limits:
            memory: "200Mi"
            cpu: "200m"

deploy2.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: woof
  namespace: default
spec:
  template:
    spec:
      containers:
      - image: nginx
        name: nginx
        resources:
          requests:
            memory: "400Mi"
            cpu: "400m"
          limits:
            memory: "800Mi"
            cpu: "800m"

overlay.yml

#@ load("@ytt:data", "data")
#@ load("@ytt:overlay", "overlay")

#! Reconfigures memory/cpu for requests and limits based on user's input
#@ def reconfigure_resource(old, new):
#@   if new == "":
#@     return old
#@   else:
#@     return new
#@   end
#@ end

#@ if data.values.resource_management:
#@ for r in range(len(data.values.resource_management)):
#@overlay/match by=overlay.subset({"kind": "Deployment", "metadata": {"name": data.values.resource_management[r].name, "namespace": "default"}})
---
spec:
  template:
    spec:
      containers:
      #@overlay/match by=overlay.all, expects="1+"
      #@overlay/match-child-defaults missing_ok=True
      -
        resources:
          requests:
            #@overlay/replace via=lambda old, new: new or old
            memory: #@ data.values.resource_management[r].requests.memory
            #@overlay/replace via=lambda old, new: new or old
            cpu: #@ data.values.resource_management[r].requests.cpu
          limits:
            #@overlay/replace via=lambda old, new: new or old
            memory: #@ data.values.resource_management[r].limits.memory
            #@overlay/replace via=lambda old, new: new or old
            cpu: #@ data.values.resource_management[r].limits.cpu
#@ end
#@ end

schema.yml

#@data/values-schema
---
#@schema/nullable
resource_management:
  - 
    #@schema/validation one_of=["meow", "woof", "quack"]
    name: ""
    #@schema/nullable
    requests:
      #@schema/nullable
      memory: ""
      #@schema/nullable
      cpu: ""
    #@schema/nullable
    limits:
      #@schema/nullable
      memory: ""
      #@schema/nullable
      cpu: ""

values.yml

#@data/values
---
resource_management:
  - name: "meow"
    requests:
      memory: "111Mi"
      cpu: "111m"
    limits:
      memory: "222Mi"
  - name: "woof"
    requests:
      memory: "555Mi"
    limits:
      memory: "5555Mi"