In Odoo 15:

First import models from point_of_sale

Then load the model skit.step.discount from python and get fields like id, discount_percentage, discount_name, is_fixed_discount and product_id.

In odoo15 models are loaded in js code.

var models = require('point_of_sale.models');

models.load_models({

model: 'skit.step.discount',

domain:[condition],

fields: ['id','discount_percentage','discount_name','is_fixed_discount','product_id'],

loaded: function (self,discount) {

self.discount = discount;

(condition)

},

});

});
In 

Odoo16:

•  In odoo16 skit.step.discount models are loaded in python code.

def _pos_ui_models_to_load(self):

         result = super()._pos_ui_models_to_load()

         result+ = ['skit.step.discount']

         return result

•  skit.step.discount models fields, domains are loaded in python code.

def _loader_params_skit_step_discount(self):

    return{

      'search_params': {

    Domain:[condition],

'fields': ['id','discount_percentage','discount_name','is_fixed_discount','product_id'],

       }

}       

def _get_pos_ui_skit_step_discount(self, params):

              return self.env['skit.step.discount'].search_read(**params['search_params'])

•  loaded model in js file.

const NewPosGlobalState = (PosGlobalState) => class NewPosGlobalState  extends PosGlobalState {

    asyn _processData(loadedData) {

await super._processData(arguments):

this. skit_step_discount = loadedData['skit.step.discount '];

     }

   }

            Registries.Model.extend(PosGlobalState, NewPosGlobalState);